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Success from Failures

David Smith, ICPI Technical Director

The sine qua non of pavement research and design

Most progress in pavement design comes from failure. For accurate and predictable pavement design, pavements must be damaged and eventually rendered useless by repeated truck wheel loads to understand where that point lies. In fact, modern highway pavement design was originally based load testing from trucks conducted by the then American Association of State Highway Officials in the 1950s. The notion of 18,000 lb (80 kN) equivalent single axle load as the basis for loading in pavement design emerged from these tests. Among many things, this testing discovered Miner’s Law, i.e., doubling wheel loads increases pavement damage to the fourth power. The exponential relationship between wheel loads and pavement damage is why truck owners pay high road use taxes; trucks do the most damage.

Since the 1950s, machines were invented that apply truck wheel loads (or greater) without drivers and do this quickly. These large machines go by different names that all render 20 years of wheel loads in a matter of months; accelerated load facility, heavy vehicle simulator, etc. Often housed at universities connected to state departments of transportation, or housed by the latter, these machines have tested thousands asphalt and concrete pavements. This research via load testing is the norm for conventional pavements. Testing led to longer-lasting designs, most of it funded by tax dollars. Such research superbly uses tax resources because of the huge ROI to road networks costing billions since accelerated load testing is typically in the millions.

For permeable interlocking concrete pavements or PICP, accelerated load testing validated ICPI design tables for subbase thicknesses published in 2011. Load testing was conducted in 2014 by the University of California Pavement Research Center in Davis (see picture below). The design tables developed by the Center with help from mechanistic modeling provide for slightly thinner bases in some situations than those in the ICPI design tables. Accelerated load testing doesn’t come cheap: the testing at Davis cost about $400,000, co-funded by the ICPI Foundation, California paver manufacturers and the Cement Association of California and Nevada.

Institutionalization from this industry investment include Caltrans PICP design tables in their pervious pavement literature, and in the ASCE national PICP standard. While the testing certainly confirmed that heavy trucks can repeatedly traverse PICP, additional accelerated load testing is needed using stronger subbases thereby expanding PICP use to busy urban streets, while storing and infiltrating stormwater.

While there has been accelerated load testing (mostly in the 1980s) of interlocking concrete pavements (ICP) here and overseas, they have taken mostly an experiential, empirical path toward validation of their structural capacity. Validation has come from millions of square feet used in airfield and port applications seeing wheel loads as much as 10 times greater than trucks. For road applications, some of the busiest downtowns have seen repeated bus and truck traffic. Downtown North Bay, Ontario and San Antonio, Texas are examples. Built in 1983, North Bay is likely approaching 4 million standard axle loads and San Antonio around 3 million, built in 1986.

While experience is informative, the interlocking concrete pavement industry might consider systematic full-scale load testing to undergird current structural design methods. A multimillion-dollar investment will put ICP in the same testing league that refined conventional asphalt and concrete pavements over the past several decades. ICP accelerated load testing will instill immeasurable confidence in designers, boost the industry’s technical credibility, and help lead to institutionalization by government road agencies and civil engineers. Like the PICP load testing, funds for ICP load testing will likely come from industry and not tax dollars, since there aren’t yet hundreds of miles of ICP roadways owned by municipal or state transportation agencies.

Success in expanding ICP road applications will come from taking ICP to the point of failure via accelerated load testing. Testing to failure is the sine qua non of pavement research and design. This can add further fuel to justifying lower life cycle costs from investing in ICP.

Above: Load testing on PICP needs to continue, and also expand to ICP.

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Change Agents

David Smith, ICPI Technical Director

There are four things that change people: books read, people met, beauty and pain. Sometimes two, three, or four of these converge on a person’s experience at the same time, and that often accelerates changes, hopefully in a positive rather than a negative direction. What have you read that crystallized or changed your thinking, beliefs and behaviors? What people have you met that brought inspiration, direction, or just simple and salty advice that you followed? What beauty have you seen in other people or provided it to others, as well as seen it in nature or in the built environment? What pain has wounded or purged you? Many of these change agents arrive when we least expect them, or when we are expecting a particular outcome and it turns into something else, and often outside of our control.

A great part of the segmental concrete paving industry is it creates beauty, intentional or not. In the early 2000s, the Port of Oakland chose 5 million sf of interlocking concrete pavement because a shipper wanted a durable pavement that could accept any type of heavy container handling equipment. Heavy means over eight times the wheel loads of highway trucks. But when you stand in this ocean of pavers covered with shipping containers, it still whispers an industrial beauty.

Segmental concrete pavement is often selected due to its beauty as well as its practicality. This is the case for winners of the Hardscape North America Project Awards. Beauty is their calling card; their practicality justified the expense. The winners also affirm the top drawer technical capabilities of manufacturers and installation contractors.

What’s most interesting is that their beauty becomes a place for meeting people, getting to know folks or just being with family. For some projects, they are places to retreat and escape to read a book, even reading one that might change life’s trajectory for the better.

What’s even more interesting is the larger site context in which each project is found. Several clearly are discovered by surprise by turning a corner and stepping or driving into a designed place. Yes, de-signed places, meaning you don’t need signs or written instructions on how to use and enjoy it. You are not in control, the place you’re in is. Sometimes, designs are so strong that controlling your relation to it and the people there isn’t a priority. That can help make the soul receptive to engage other people, books, beauty and, yes, pain, all of which might yield an epiphany. On behalf of the HNA Awards winners, we are delighted to present places that can be such change agents.

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Missionary Work

David Smith, ICPI Technical Director

State departments of transportation (DOTs) rely on millions of tax dollars for road construction and maintenance. They also look after thousands of structures including bridges. For decades, DOTs are immersed—and one might say entrenched--in design, maintenance and improvement of asphalt and concrete pavements. These are mostly highway pavements.

Most DOTs look after local roads as well, especially if they are national or state routes passing through a city or town. About one fourth of all roads are urban, so some portion of this percentage is under state DOT care. While the percentage of their total road inventory likely varies from state-to-state and province-to-province, urban roads represent an opportunity for interlocking concrete pavements (ICP).

Here is a story from the New York State DOT (NYSDOT) who made a new path for ICP. In 2004, the U.S. Federal Highway Administration contacted the NYSDOT requiring removal of ICP from pavement use due to crosswalk failures. This was likely a federally funded road project. In the fall of 2005, at the request of the industry, a task force was created to implement new specifications and subbase requirements to allow ICP.  

In 2006, provisional ICP specifications were written with drafts of typical sections for ICP crosswalks in high use areas. The drafts included a 12-inch thick crushed stone subbase, 8 inches of concrete, ¾ inch sand-bitumen setting bed and adhesive under 3 1/8-inch thick (80 mm) thick pavers in a herringbone pattern. Interestingly, the paver thickness was increased from 2 3/8 (60 mm) to 3 1/8 inch as recommended by ICPI.  The NYSDOT found a trial location, where a crosswalk(s) in a street could be built. The street had about 8,000 average annual daily traffic (AADT) and provided a pilot project to monitor the success of the draft specifications.

In 2007, the State Historic Preservation Society decided that ICP must be used to replace the pavement on Main Street in East Aurora, NY. AADT was over 20,000 with 10% to 12% truck traffic. This equates to roughly 10 million equivalent single axle loads (ESALs) over 20 years assuming 1% annual traffic growth. This becomes NYSDOTs pilot project. It was built in 2009 with five lanes, curb to curb ICP for about 4 blocks or about 1000 feet. The project involves over 250,000 pavers or over 55,000 sf.

Above: Four blocks of interlocking concrete pavement are paved on Main Street in East Aurora, New York in 2009.

After three years of monitoring, the pilot project was deemed acceptable in 2012. NYSDOT issued a new Standard Specification 601 for Architectural Pavements (see their 2016 Standard Specifications Section 601), as well as standard drawings (sheet M601-01 in the 2015 collection of New York State Standard Sheets). In 2017, the East Aurora ICP continues to perform well with the additional blessing of no utility cuts in the pavement.

Above: Main Street in 2014.

The diligence of an NYSDOT advocate, Jim Patnaude, Associate Engineering Materials Analyst, Materials Bureau in Albany, was a prerequisite to the industry becoming involved. While the state specification is only for concrete bases, it is a start. The next step might be writing design guidance and specs for lower traffic areas that include less expensive, dense-graded aggregate bases and those stabilized with asphalt or cement. While design guidance for these areas is available in a national design standard (see ASCE 58-16 Structural Design of Interlocking Concrete Pavement for Municipal Streets and Roadways), DOTs would embrace ICP more readily if the industry committed to full-scale load testing. This type of validation is done daily by several DOTs and universities across the U.S. and Canada for asphalt and concrete pavements. Since DOTs have great influence on municipal road specifications, this investment could make DOT and industry missionary work on local road applications turn into a Reformation.    

Above: Main Street in 2017.

Photos are courtesy of Jim Patnaude, NYSDOT.  

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You Have to Think

David Smith, ICPI Technical Director

As we enter the 25th year of ICPI, the industry returns to pre-recession sales levels. Residential sales dominate about three-quarters of shipments, with the remainder placed in commercial (specified) applications. Permeable interlocking concrete pavements, paving slabs and planks are the high-growth products. Permeable units have been regulated into existence, whereas slabs and planks present a sleek, modern aesthetic that visually and emotionally connects pedestrians to residential and commercial settings.

While the economy charges forward and pulls construc­tion with it, we continually remind users that segmental concrete pavement products are elements or components within larger pavement systems. The systems con­sist of hundreds of possible combinations of elements: paving units, patterns, colors, bedding and base materials. Traffic and soils often drive the right combinations. Like any other pavement or build­ing system, finding the right combination of elements for an application is the key to ease of construction and minimal maintenance.

ICPI provides a large stable of detail drawings and specifica­tions on www.icpi.org to help designers choose the best combination of elements. Twenty-three ICPI Tech Specs offer design, construction and maintenance advice on a range of assemblies. However, they don’t cover absolutely every design situation. There­fore, some thinking is required to find the assembly that fits the application while avoid­ing cut-and-paste solutions. More importantly, thought and study are required to understand the interaction of pavement materials under different loads and in vari­ous climates. In a fee-driven, hurry-up design and construc­tion world, clear thinking about segmental pavement can get overlooked.

Some decision tools are needed to bring clarity to design thought processes. One segmental paving expert who provided an integrated decision tool for many ap­plications is Professor John Knapton on www.sept.org/techpapers/1098.pdf. Entitled, “A Total Quality Approach to Pavement Specification,” the paper was written 17 years ago and provides a structure for decision-making regarding selecting the right pavement structure components. An­other summary of structural performance and system as­semblies are presented below as a guideline. We hope these clarify your thinking.

Assembly Selection Guide

Structural Performance Limits

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Deciphering Planks, Slabs and Pavers

David Smith, ICPI Technical Director

An increasing number of segmental concrete paving projects include planks, also known as linear pavers. In preparation for eventually developing ASTM and CSA product standards, an initial task for the industry was developing a product definition differentiating planks from slabs and pavers. The intent here is to decrease and eventually remove the interchangeability of these product terms. To achieve this, the following definition for planks was recently provided by the Interlocking Concrete Pavement Institute:

Finished (exposed) face area ≤ to 288 in.2 (0.185 m2)

Length divided by thickness ≥ than 4

Length divided by width ≥ 4

Minimum thickness of 2.36 in. (60 mm)

Minimum length of 11.75 in. (298 mm)

Maximum length of 48 in. (1220 mm)

Minimum width of 2.5 in. (63 mm)   

This definition frames a dimensional envelope that distinguishes planks from paving slabs and from interlocking concrete pavers described in ASTM and CSA product standards. To better understand the differences, product definitions for slabs and pavers are provided below for comparison. Compared to ASTM C936, the CSA paver definition allow for slightly larger units in length and width: 11.8 x 11.8 in. or 300 x 300 mm units. Such units need to be at least 75 mm or almost 3 in. to meet the CSA definition of a paver.

The Dividing Lines

In practical terms, what separates planks from pavers are length and thickness. Shorter and thicker units (pavers) see better performance in vehicular traffic because they aren’t as subject to as much bending forces, thereby lowering risk of cracks under tires. A dividing line between planks and pavers is illustrated in the table below with a 3 x 12 x 3.125 in. thick paving unit. Some might think it’s a plank but is not. The unit is a concrete paver that meets C936 and CSA A231.2 definitions.

In addition, its length divided by thickness or aspect ratio is 4, making it acceptable for limited vehicular traffic such as a residential driveway. If the unit was thicker, say 4 in., the aspect ratio would be 3, thereby capable of accepting parking lot and roadway traffic. In contrast, a 3 x 12 in. unit with thickness of 2.36 in. or 60 mm has an aspect ratio of 5, thereby meeting the plank definition. This unit should be used in pedestrian applications only.  

The bottom line is that dividing lines define dimensional envelopes. They have implications on whether to apply them in vehicular traffic and how much. The how much question was answered in the winter issue of the Interlock Design magazine’s editorial column. If you’d like to access it now, put www.icpi.org/IDApp into your cell phone and download the new Interlock Design app for Android or Apple devices or visit the archives page at www.icpi.org/interlock-design-archives.

Above: Slabs

Above: Planks

Above: Pavers

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The Use of Geotextile in Permeable Pavement

Robert Bowers, P. Eng., ICPI Director of Engineering

ICPI Director of Engineering, Robert Bowers, P. Eng., receives questions from members in need of advice and tips regarding permeable paver driveways.

One recent question referred to a residential permeable pavement driveway, and when to use geotextile versus when to not.

Sometimes called filter fabric, geotextile is made of synthetic fibers formed into a sheet that are designed to allow water and gases to pass through them, while retain soil particles. Geotextile separates and contains the base from the underlying soil subgrade. It allows the base to shed water, and prevents the soil around it from working its way into the base.

Without geotextile, the soil will work its way into the base and weaken it. This is a slow process that happens when the soil is saturated with water or during periods of thawing. Geotextile stops this process and extends the life of the base by many years. Geotextile is recommended for use over silt and clay soils. It is not essential in sandy soils.

The decision to use a geotextile in permeable pavement should be based on the same criteria used when considering use of a geotextile for the traditional interlocking concrete pavement: 1) confinement of the base aggregate and 2) separation of the base aggregate from the subgrade soil. Confinement and separation created by the geotextile will help ensure that the base in a pavement system will function longer than a base that is not wrapped in a geotextile.

However, the selection criteria also requires that the geotextile have a high level of permeability. Typically, geotextile manufactures report the materials ability to pass water through it as the permittivity. The greater number, the faster water will pass through.

The member went on to ask if they should use the same woven geotextile as specified for traditional paver systems?

If the soil is structurally sound, like a sand-gravel mixture, the use of non-woven needle punched geotextile should work. It was suggested that a thicker non-woven needle punched geotextile, such as an 8 oz., be used because of the damage it would experience from compacting larger angular aggregate on top of it.

If the soil is weaker, like silt or clay, the use of a woven geotextile would be appropriate. However, it was recommended to look for a geotextile with a higher permeability to allow the water collected in the system to pass through the geotextile and infiltrate in the subgrade unimpeded. Typical slit-tape woven geotextile would not be suitable because of its low permittivity. It is recommended to use a mono-filament, multi-filament or fibrillated-filament type woven geotextile.

Have an engineering or technical question? Robert is always ready to respond with the latest technical resources and information.

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The Effects of Deicing Chemicals on Interlocking Concrete Pavers

David Smith, ICPI Technical Director

Winter is coming...learn about the effects of deicing chemicals on interlocking concrete pavers.

Interlocking concrete pavements are a flexible and durable system that performs successfully in the most demanding applications, conditions and climates. One of the more extreme conditions is the application of deicing chemicals to prevent or reduce ice buildup which can contribute to slips, falls and loss of vehicular control. This Technical Note outlines factors that contribute to a low risk of damage from deicing materials on concrete pavers. 

Unit Properties Impacting Paver Durability

Ice that may form and expand inside the paver can cause stresses that may lead to degradation. Deicing materials mixed with the ice can increase the damage potential. Properly manufactured concrete pavers, however, are very durable and resistant to degradation because the high density of a paver limits deicing materials from entering. In addition, a high cement content helps a paver resist damage from the stress of expanding ice. Research and experience have highlighted factors affecting the winter durability of concrete pavers, including the utilization of:

Aggregates with low absorption that will not degrade when subject to freezing and thawing and deicing materials;

Proper aggregate gradation that allows for high density compaction;

Sufficient cement paste to coat the aggregate and reduce capillary pores; and

Sufficient compaction during manufacturing to ensure maximum density and uniformity.

Units manufactured with these characteristics typically yield a high density, low absorption, high compressive strength, resulting in a durable paver.

ASTM C936 Standard Specification for Solid Concrete Interlocking Paving Units includes freeze-thaw durability criteria for assessing the freeze-thaw durability and resistance to deicing salts. C936 references the test method ASTM C1645 Standard Test Method for Freeze-thaw and De-icing Salt Durability of Solid Concrete Interlocking Paving Units. C936 includes an optional lower freezing temperature for regions of the United States that experience severe freezing conditions based on a climatic zone map. The optional testing in 3% saline for these regions is equivalent to the testing required in the Canadian concrete paver standard, CSA A231.2 Precast Concrete Pavers. To obtain a copy of ASTM C936 or ASTM C1645 visit www.astm.org (link is external). The CSA standard is available from www.csagroup.org (link is external).

Comparison to Ready Mixed Concrete

Properly air-entrained and finished ready-mix concrete can resist freeze-thaw degradation, although over-finished, cast-in-place slabs or those made with re-tempered concrete with too much water can be susceptible to surface scaling. Compared to ready-mixed concrete, concrete pavers have the following advantages when exposed to freeze-thaw conditions and deicing agents:

Stronger aggregate bonding from higher cement content than typically used in pavement quality ready-mix concrete;

Smaller aggregates (more surface area for the cement to bond);

Lower water/cement ratio as well as vibration and compaction during the manufacturing process to increase aggregate-cement contact and to eliminate the possibility of over-watering;

Produced in a highly controlled manufacturing plant leading to lower variation in material properties with elimination on over-finished surface; and

Can be successfully installed in cold weather because they are properly cured before they leave the manufacturing plant.

Research prepared for the Utah Department of Transportation* in 2013 found that concrete exposed to sodium chloride experienced only minor, if any, adverse effects, while specimens exposed to calcium chloride, magnesium chloride, or calcium magnesium acetate (CMA) experienced significant deterioration, including scaling, cracking, mass loss, and compressive strength loss. While the literature review did not specifically address unit pavers, the findings are directly related to cured unit concrete properties. The report recommends that engineers responsible for winter maintenance of concrete pavements should utilize sodium chloride whenever possible, instead of calcium chloride, magnesium chloride, or CMA, and apply only the amount absolutely necessary to ensure safety of the traveling public. These findings support ICPI's guidelines for deicing salt exposure.

*Physical and Chemical effects on Deicers on Concrete Pavement: Literature Review, Report No. UT-13.09 Prepared for Utah Department of Transportation Research Division by Brigham Young University, July, 2013

Guidelines for Limiting Deicing Chemical Exposure

A key to successfully using deicing materials on unit concrete pavers is using only as much as needed to do the job. This will maximize their benefits while minimizing any damage to the concrete pavers and surrounding environment. The following guidelines can help limit the exposure of deicing chemicals while maintaining a safe environment:

Apply sand first to increase traction, then apply deicers as needed. Sand should not be applied to permeable interlocking concrete pavements.

Rock salt (sodium chloride [NaCl]) is the least damaging to concrete materials and should be used whenever possible.

If a more effective, quicker acting deicer is necessary, consider the judicial use of calcium chloride.

The use of magnesium chloride or CMA is not recommended because they can chemically degrade all types of concrete, significantly increasing potential damage. The potential for damage from CMA increases with the amount of magnesium in the formulation.

Do not over apply deicing chemicals; follow the recommended dosage.

Do not use deicing chemicals in place of snow removal but reserve them for melting ice formed by freezing precipitation or freezing snow melt.

Once loosened, snow, ice and excess deicing salts should be promptly removed by plow or shovel to avoid a buildup in concentration of the deicing chemical(s).

Protect vegetation and metal from contact with deicing chemicals as most can impair vegetation and corrode metals.

In addition, use ICPI-recommended jointing and bedding sand materials to minimize water penetration into the pavers. This can also help reduce salts from entering and accumulating in the jointing and bedding sand that may eventually degrade the pavers. ICPI also recommends adequate pavement slopes (typically a minimum of 2%) to facilitate surface water drainage and help remove deicing materials. While not essential, reduction of water entering jointing sand can be further enhanced with joint sand stabilization materials and/or sealers.

Deicing Chemical Comparison Chart

The following chart compares common deicing chemicals with respect to their effective temperature, plus their impact on the potential freeze-thaw degradation and on chemical degradation of the concrete.

*Effective temperature is lowest practical temperature of the deicer defined as the lowest temperature at which the relative melting potential (MP) is 0.7 as calculated in reference 1 below. ¹ Information adapted from National Cooperative Highway Research Program Report 577 "Guidelines for the Selection of Snow and Ice Control Materials to Mitigate Environmental Impacts" ©2007 Transportation Research Board

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Silica FAQs

Robert Bowers, P. Eng., ICPI Director of Engineering

ICPI Director of Engineering, Robert Bowers, P. Eng., receives questions from members in need of advice and tips regarding silica.

The following questions arose from the participants in the recent ICPI webinar, "Preventing Silica Exposure of the Jobsite." After consultation with the presenters, Rob Bowers summarized these responses.  The webinar recording is available on the Webinars and On-Demand Learning page. The recording is FREE to members as part of the Contractor Webinar Series and costs $70 for non-members.

Respirable Crystalline Silica References

ICPI's statement regarding OSHA Silica Standard dated September 25, 2017 - https://www.icpi.org/newsroom/osha%E2%80%99s-occupational-exposure-crystalline-silica-rule-force

Small Entity Compliance Guide for the Respirable Crystalline Silica Standard for Construction  (link is external)

Small Entity Compliance Guide for the Respiratory Protection Standard (link is external)

Online tool to Develop a Respirable Crystalline Silica Exposure Control Plan provided by The Center for Construction Research and Training - https://plan.silica-safe.org/ (link is external)

Sample Respirable Crystalline Silica Exposure Control Plan provided by Zurich Insurance North America (link is external)

Occupational Safety and Health Administration Standard 29 CRF

Table 1: Specified Exposure Control Methods When Working With Materials Containing Crystalline Silica

29 CFR Parts 1910, 1915, and 1926 Occupational Exposure to Respirable Crystalline Silica; Final Rule as published in the Federal Register (link is external)

Part 1910 Occupational Safety and Health Standards, Subsection 134 - Respiratory Protection  (link is external)

Part 1910 Occupational Safety and Health Standards, Subsection 1053 - Respirable crystalline silica (link is external)

Part 1926 Safety and Health Regulations for Construction, Subsection 1153 - Respirable crystalline silica (link is external)

Answers to Post-Webinar Questions:

1. Is there a template available we can follow to implement the safety program/manual for silica? Currently, contractors can make use of the following generic construction industry tools.

Online tool to Develop a Respirable Crystalline Silica Exposure Control Plan provided by The Center for Construction Research and Training (link is external)

Sample Respirable Crystalline Silica Exposure Control Plan provided by Zurich Insurance North America (link is external)

2. Regarding OSHA's statement that certain tasks on table one do not require medical monitoring IF an employee does not perform that or other tasks which require an APF 10 for more than 30 days...Do we have an interpretation of is that 30 instances or a total of 30 days with more than 240 hours of work exposure (totaling 30 days)? The Small Entity Compliance Guide states, “Employers must make an initial or periodic medical examination available to employees who will be required by the silica standard to wear a respirator for 30 or more days per year in the upcoming year (the next 365 days). "If the employee is required to wear a respirator at any time during a day, even if it is just for a few minutes, that counts as one day of respirator use.”

If an employee is required to perform a task that requires a respirator, as a contractor and employer, you will be required to comply with the related OSHA Standards. a. A Respiratory Program per 29 CFR 1910.134 Federal OSHA Standard. The Respiratory Program includes:

Medical evaluation questionnaire

PFT – Pulmonary Function Test

Respirator fit test

Written respiratory program with documented training

b. In addition, the Silica Standard 29 CFR 1910.1053 and 29CFR 1926.1153 program requirements include the respiratory program listed above AND the following:

Physical Exam

TB Test

Chest X-Ray – must be read by a NIOSH-certified B Reader

Written silica exposure control plan with documented training

3. Does the IQ saw meet the requirement of not having to have a respirator for a standard paver cut and is there written data to support the requirement which can be used as part of an employer’s written silica exposure control plan? iQ Powertools has reported they have objective air monitoring test data to confirm that the tool, when used per manufacturer’s recommendations, meets the OSHA Silica Permissible Exposure Limit (PEL). Contact iQ Powertools to obtain this test data.

When a manufacturer tests its equipment, if the work practice and materials used match the job site conditions, OSHA will allow this data to be used as objective data as part of a written silica exposure control plan. Remember, to comply with the standard, OSHA requires an employer to have a written silica exposure control plan.

Since cutting concrete with a vacuum assisted saw is not listed in Table 1 of the standard, the employer must follow the Alternative Exposure Control Methods to determine the levels of respirable crystalline silica that employees are exposed to. This can be done using the performance option; or the scheduled monitoring option as directed by the standard. Following the performance option will require Objective Data that demonstrates employee exposure to respirable crystalline silica associated with a particular product or material or a specific process, task, or activity. The data must reflect workplace conditions, that closely resemble, or could result in higher exposures, than the processes, types of material, control methods, work practices, and environmental conditions in the employer’s current operations.

Examples of objective data are information such as: a. Air monitoring data from industry-wide surveys; b. Calculations based on the composition of a substance; c. Area sampling results and exposure mapping profile approached; and d. Historical air monitoring data collected by the employer.

4. Do smaller residential projects have the same rules and regulations as larger commercial projects? Yes. The Federal and state OSHA standards apply to all employers, large and small, nationwide. It applies to all projects, large and small, nationwide. In the past, you may have worked on smaller residential projects and never saw an OSHA inspector. Smaller residential projects are harder for them to find. But, if they drive by and see you working, they will probably stop and do an inspection. ICPI recommends that you be prepared, comply with the standard, have a silica exposure program in place and protect the health of your workers.

5. What about homeowners that are working on their own homes? OSHA standards do not apply to homeowners working on their own property or to contractors who work by themselves. “29 U.S.C. § 654, 5(a)1: Each employer shall furnish to each of his employees employment and a place of employment which are free from recognized hazards that are causing or are likely to cause death or serious physical harm to his employees.” The caveat is that OSHA does not cover workers who are not employees. However, OSHA has determined that exposure to respirable crystalline silica at a level under 50 µg/m³ over an eight-hour period time weighted average (TWA) is a safe Permissible Exposure Limit (PEL). It would make sense that homeowners and single contractors not jeopardize their health and work to be below the PEL.

6. What if you are using a table saw but dry cutting with a vacuum attached? a. Is this acceptable? As mentioned above, dry cutting concrete with a vacuum system is not listed in Table 1 so you would have to comply with the Alternate Exposure Control Methods. Determining if this would reduce the exposure level below the Permissible Exposure Limit (PEL) can only be determined after Air Monitoring Data is collected using a worker performing that task with the equipment, materials and site conditions in question. It may be possible to confirm the operator, and those in the immediate area, are safely under the Permissible Exposure Limit (PEL), if you have objective test data.

b. Can you use a respirator in addition to the vacuum? Use of a respirator will reduce the exposure level by the respirator’s Assigned Protection Factor (APF). As an example, if a worker is exposed to an environment that has a measured respirable crystalline silica level of 400 µg/m3 per 8-hr day TWA and they use a respirator with an APF of 10, the calculated exposure level will be 40 µg/m3 per 8-hr day TWA which is less than the regulated PEL. However, if the worker uses a respirator for more than 30 days a year, they will have to comply with 29 CRF 1910.134 - Respiratory Protection. In addition, the employer must comply with the additional respirator requirements from the Silica Standard. (See Question 2.b)

7. I thought I was told that none of the tools present in today’s markets provide the necessary filtration to ensure compliance with the new PEL limits. a. Is this true? False. There are many tools with vacuums attached or integrated, from various manufacturers, that could be used to drill, grind, chip, and cut concrete, asphalt and masonry materials that will safely keep an employee under the 50 µg/m³ over an eight-hour period time-weighted average.

b. If so, then even if you have vacuum saws you must then have respirators? The tools available are getting better and better at reducing the exposure to respirable crystalline silica. If it can be demonstrated with Air Monitoring Data collected using a worker performing the task with the equipment, materials and site conditions in question, that exposure levels are below the Permissible Exposure Limit (PEL) then a respirator is not required. However, if the dust reduction systems are not function at 100% effectiveness or the conditions change from those present when the Air Monitoring Data was collected, it is possible that an OSHA inspection could conduct a test and determine the exposure level is more than the PEL. That is why ICPI recommends when cutting concrete with a saw, the use of a respirator is a good practice.

8. When OSHA’s Table One does not give specific control method of using a commercial vacuum system for some tasks, and does for others, may we assume we can use a commercial vacuum system IF we obtain test results, as OSHA outlines, that would prove we can perform the task below the PEL? Yes. As mentioned previously, if the exposure control method is not included in Table 1, the Alternate Exposure Control Method must be utilized. Table 1 currently does not include dry cutting concrete with a saw using a vacuum dust reduction system. The first step of the alternative exposure control method is to determine the levels of respirable crystalline silica that employees are exposed to. This can be determined by collecting Air Monitoring Data using a worker performing that task with the equipment, materials and site conditions in question. These results may prove the exposure levels are below the Permissible Exposure Limit (PEL) and even the Actionable Exposure Limit (AEL). However, it will still be necessary to comply with the Alternate Exposure Control method and, “use engineering and work practice controls, to the extent feasible, to limit employee exposures to the PEL, and supplement the controls with respiratory protection when no other alternative is available. As well as keep records of employee exposure to respirable crystalline silica.”

9. Does the protection requirement pertain to just the individual using the saw to cut & not installers that are not in the immediate area? Part of the written control program should contain information on methods used to restrict access to the area. The plan must include a description of the procedures used to restrict access to work areas, when necessary, to limit the number of employees exposed to respirable crystalline silica and the levels to which they are exposed, including exposures generated by other employers or self-employed workers. When Table 1 requires respiratory protection, employers must provide respirators to all employees engaged in the task.

It would make sense that persons working in the restricted area would need the same level of protection afforded to the worker whose task was generating the respirable crystalline silica.

10. How do you perform an air monitoring test? An air monitoring test is typically conducted using the following equipment: Air sample pump, calibrator or rotameter, air sampling cassette filter, cassette filter holder, cyclone, tubing and clip. A small tube runs from the pump over the shoulder and is clipped on the chest or collar near the worker’s breathing area. This test can be done with or without a respirator. The worker them performs the task that needs to be analyzed. As the pump runs, air taken from the vicinity of the worker’s breathing area is filtered to collect all dust present. Once the testing is complete, the length of time the pump runs and the volume of air sampled is then recorded. The cassette filter is then analyzed in a lab to determine the mass of respirable crystalline silica captured. This number is then factored to consider the volume of air the worker would breathe in an 8-hour day compared to the volume of air sampled by the pump over the period of time that the air sample was taken.

Here is a link to a video from ALS Global that will be useful to contractors wanting to understand how to use air monitoring equipment to perform a test themselves: https://www.youtube.com/watch?v=O5knJEGGa7k (link is external)

11. Isn't it true that the current studies show that even cutting with a vacuum saw or wet you still would be required to have a respiratory system? There are numerous studies that have been done with results both above and below the Permissible Exposure Limit (PEL). Remember, if an employer has objective test data to confirm the tools, work practices and materials being used, creates and exposure level under the Permissible Exposure Limit (PEL) then no respirator is required.

The intent of the OSHA Silica Standard is to limit employees’ exposure to silica and keep them in a safe work environment. OSHA has determined that 50 µg/m³ over an eight-hour period time-weighted average (TWA) is a safe, maintainable limit.

12. Does an N95 Mask count as a respirator? Yes. OSHA recognizes the N95-rated, 2 strap mask as a respirator with an Approved Protection Factor (APF) of 10. Please reference OSHA’s Small Entity Compliance Guide for the Respiratory Protection Standard as well as 29 CRF 1910.134 - Respiratory Protection standard. As with any respirator, they must be fit tested. Refer to Question 2 for more information regarding a respiratory program.

13. What about Techniseal NextGen? Techniseal’s NextGel stabilized joint sand is reported by the manufacturer to generate substantially less dust when it is spread and compacted into the joint compared to other joint sand. Obtaining objective data from the manufacturer could confirm this. Alternately, collecting Air Monitoring Data using a worker spreading and compacting the joint sand with the equipment, materials and site conditions in question would be needed to confirm the exposure level.

14. What is the contact information for lab that does air monitoring testing? There are three main components to get Objective Data, i.e. a silica air monitoring test report.

Obtain air monitoring equipment (air pump, calibrator, air sampling cassette, hoses and a clip)

Conduct air monitoring tests – which is typically done by Industrial Hygienists.

Analyze the collected samples.

Here are links to two Industrial Hygiene companies that can help you obtain Objective Data.

Galson Labs – Air Sampling Equipment Rental and air sampling and analysis http://www.sgsgalson.com/ (link is external)

EMSL Analytical, Inc. – Provides Industrial Hygienists and air sampling & analysis https://www.emsl.com/ (link is external)

15. Are there procedures to clean up after cutting pavers? a. If wet cutting, what is the suggested clean up procedure of the slurry? If you are using a wet table saw, remove the slurry from the saw and allow it to dry, solidify and then dispose of with other site waste. Handle with care as to not reintroduce the dust into the atmosphere where it could be inhaled by someone. If cutting in place with a saw that has a water attachment and the slurry is on the paver surface, use large volumes of water to rinse before the slurry dries and permanently stains the paver surface. Scrub with a stiff bristle brush if necessary.

b. Once dust is collected, what is the procedure for proper disposal? The Housekeeping section of the standard requires that when cleaning up dust that can contribute to employee exposure to respirable crystalline silica, employers must:

Not allow cleaning by dry brushing and sweeping, unless methods such as wet sweeping and HEPA-filtered vacuuming are not feasible;

Not allow cleaning of surfaces or clothing with compressed air, unless the compressed air is used together with a ventilation system that effectively captures the dust cloud or no other cleaning method is feasible.

This section of the written plan would include cleaning methods that are acceptable (e.g., wet sweeping), cleaning methods that are unacceptable because acceptable cleaning methods are feasible (e.g., dry sweeping or blowing), and special instructions (e.g., use local exhaust ventilation if compressed air must be used). Hygiene-related subjects, such as not using compressed air to clean clothing, could also be addressed in this section of the written exposure control plan.

Remember the intent of the OSHA Silica Standard is to limit employees’ exposure to silica and keep them in a safe environment. Care and common sense apply to the proper disposal of the collected dust. Do not reintroduce the dust into the atmosphere where it could be inhaled by someone. Here are some options.

Mix the collected dust with water and allow to dry and solidify, then dispose of with other site waste.

Put the collected dust into a sealed container or trash bag for disposal with other site waste.

Mix it with moist native soil on the job site.

Additionally, the paver industry has used the terminology “sweeping” joint sand. To help differentiate the clean-up task from the necessary interlocking concrete pavement construction step, it is suggested that you use the terminology “applying” or “spreading” joint sand. Use of the term sweeping will probably attract unnecessary attention from an OSHA inspector because of the almost complete prohibition on dry sweeping. Keep in mind, the Permissible Exposure Limit still needs to be considered.

Have additional questions regarding silica? Please contact ICPI, at 703-657-6900.

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Getting to the Root of the Problem

Robert Bowers, P. Eng., ICPI Director of Engineering

Getting to the root of the problem. ICPI Director of Engineering, Robert Bowers, P. Eng., receives questions from members in need of advice and tips regarding the best practices to use when constructing paver driveways.

One recent questions referred to a residential driveway. A client wanted to install a 2,000 sf paver driveway due to the roots from 100+ year old oak trees that had damaged the existing driveway. The clients wanted a solution that would give them an attractive, stable driveway, yet would not hurt the roots of the trees.

Any cutting or compaction near the roots would result in excessive stress on the trees, possibly causing it to die a couple years, so what is the best way to install concrete pavers over existing roots without damaging the root system?

Obviously cutting the roots back to install the paver base would not be an option. Alternately, installing the aggregate base on top of the existing root mat would also present problems. Compacting the aggregate base could injure the root system. Over time the roots would grow towards the surface, through the base and bedding sand in their search for water. Eventually this would cause movement and buckling of the paver surface.

Image above: Cracking caused by tree roots (http://www.qualityincalifornia.com/2011/09/cracking-from-tree-roots.html) A better solution would be to consider a permeable interlocking concrete pavement (PICP) system. PICP is typically constructed on uncompacted subgrade. A plus for the tree roots. PICP will detain water under the pavement surface to allow it to infiltrate into the subgrade. Another plus for the trees. Tree roots also require air. In a typical PICP base, 40% of the volume is air. Again, another plus for the trees. This open volume also give the trees root plenty of space to grow before surface movements are become a problem. When you add it all up, PICP systems make sense when you consider the impact and needs of the surrounding trees.

A similar situation occurred at Louisiana State University. The landscape architect used PICP systems in areas around 200+ year old oak trees. The open graded aggregate base of the PICPs reduce the compacted forces from students walking on the soil, and PICP delivers water and air to the tree roots. The trees on campus that once showed visible signs of distress are now thriving.

Image above: LSU’s campus where PICP systems were installed to reduce the compacted forces from students.

Image above: PICP systems installed on LSU’s campus in areas around 200+ year old oak trees.

Have an engineering or technical question? Robert is always ready to respond with the latest technical resources and information.

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Couldn’t Stand the Weather

David Smith, ICPI Technical Director

Resiliency in Green Infrastructure Renovation

Mark Twain said, “Everybody talks about the weather, but nobody does anything about it.”

Global climate change might be altering the implications of Mr. Twain’s saying because we are likely doing something to the climate and maybe something about it. While the causes and effects of climate change receive endless debate in scientific and political spheres, regional-scale rainfall patterns are changing for certain. The result has been wetter weather in some parts of North America, drier in others.

The weather changes have been so dramatic that rainfall statistics defining storm recurrences are seeing realignment. A hypothetical example explains this shift. Say there are 80 years of storm data and some indicates that very occasionally, a city receives five inches rainfall in 24 hours. Some statistics are run and they conclude that the city has 4% probability of that rainfall depth occurring in any given year. So it’s called a 25-year storm. But data gathered over the past two decades now indicate a 10% probability. So that rain event has shifted to a 10-year storm recurrence. The old 10-year storm with maybe three inches of rain is now five inches.

This shift directly affects cities because storm sewers back up and can’t immediately drain the additional water. When that happens, it can end up in someone’s basement. Besides property damage, the city can be liable for damages. Storm sewers originally designed to manage a 10-year storm are now obsolete as confirmed by revised rainfall statistics.

Hurricanes plague the East, tornadoes the Midwest and South, and earthquakes the West. Because of natural disasters like the earthquakes in Northridge and Loma Prieta, and Hurricanes Katrina, Irene and Sandy, governments at all levels are seeking resilient designs and technologies to resist excessive wind, rain and tectonic plate movements. Resilient infrastructure resists these onslaughts from nature by designs that minimize damage to private property and society’s productivity. As urban infrastructure is rebuilt, resilient technologies and designs are increasingly included.

One city implementing resilient infrastructure is Atlanta, GA. It recently completed the Southeast Atlanta Green Infrastructure Project. Infrastructure renovation involved replacing century-old water lines, storm and sanitary sewers in two neighborhoods. The ‘green’ portion reduced stormwater runoff, a fundamental goal in most GI projects, with permeable interlocking concrete pavement. Atlanta went beyond reducing runoff. It installed around 700,000 sf (65,000 m²) of permeable interlocking concrete pavement with enormous water storage capacity to reduce increasing flood events.

According to Todd Hill, P.E., Atlanta’s Director of Watershed Management, the pavement stores about 7 million gallons. That approaches one million cubic feet of water in over 10 Olympic-sized swimming pools. As an extra bonus, maybe a fourth of that water is infiltrated back into Atlanta’s clay soils. A portion of the $66 million invested will be returned in spared litigation costs, not to mention increased property values and resulting taxes.

In their present state, many urban drainage systems simply can’t stand the weather. In response, resilient urban infrastructure is an intentional public investment goal. As they rebuild, cities and neighborhoods can resist bad weather by providing permeable pavements that control flooding while remaining un-flooded and useable during the worst storms. Atlanta certainly magnifies and affirms the role of permeable interlocking concrete pavement in resilient infrastructure.

Be on the lookout for the release of the ICPI Case Study, Atlanta's Resilient Green Infrastructure with Permeable Interlocking Concrete Pavement.

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ICPI Education Courses Address Urgent Need for Knowledgeable and Skilled Concrete Paver Installers

Charles McGrath, ICPI Executive Director

Seventy-three percent of the 218 segmental concrete pavement contractors who responded to the 2017 ICPI Contractor Industry Survey said recruiting/hiring quality employees was one of their greatest challenges, while only 18.6% indicated demand for their services was a top concern.

These findings reveal one obvious, but significant fact:  there is a strong market in the U.S. and Canada for concrete pavers, but the industry struggles in finding skilled employees to capitalize on this demand.

This trend is reflected throughout the wider residential construction industry.  According to the National Association of Home Builders, there were 203,000 unfilled construction jobs in April.  This fact combined with an aging construction workforce (see chart below) means that our industry may have to confront a trained worker shortage in the foreseeable future.

Image above: Graph from NAHB’s article, “Young Construction Workers Mean More Monitoring, Longer Projects.”

In response to this challenge, the Interlocking Concrete Pavement Institute (ICPI) is helping segmental concrete pavement contractors find an answer to worker shortages.  The Institute dedicates considerable resources to ensuring contractors and their employees learn the industry’s best installation practices through member-sponsored courses. From July 2016 to June 2017 ICPI and its members sponsored 89 courses across the United States and Canada.

ICPI offers beginning, immediate, and advanced courses for installers in the U.S. and Canada, including a Concrete Paver Installer course, an Advanced Residential Paver Technician course, a Commercial Paver Technician course and a Permeable Interlocking Concrete Pavement Specialist course. In all, more than 31,000 professionals participated in ICPI installer courses, including 1,833 installers from July 2016 through May 2017.  

Individuals who became ICPI Certified Concrete Paver Installers passed the Concrete Paver Installer course with a minimum of 10,000 sf of installation experience. ICPI Certified Concrete Paver Installers can be verified on the ICPI website.              

Courses for the upcoming season are now organizing. Click here for the current calendar of classes on the ICPI website (www.icpi.org), and check regularly because new classes are being launched weekly. If you are an ICPI member paver manufacturer, supplier or dealer, you can sponsor a course in your area.  Contact Anya Plana-Hutt, ICPI Manager of Education, at aplana-hutt@icpi.org to discuss sponsoring a course.

In addition, ICPI now offers members a complimentary benefit addressing entry-level installer training needs for contractors. It’s launching a quarterly demonstration video series available on-demand from the ICPI website. The first demonstration video is Basic Paver Installation.

For more information about ICPI education courses and certification, click here.

For more information about ICPI, please visit www.icpi.org. To purchase the complete 2017 ICPI Contractor Industry Report, please visit the ICPI Bookstore, www.icpi.org/shop. Contractors who participated in the survey received a complimentary copy. Retail price: $100. ICPI members pay only $25.

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Paver Patio Points

Robert Bowers, P. Eng., ICPI Director of Engineering

As the weather gets warmer, consumers start to create their outdoor dream space.

ICPI Director of Engineering, Robert Bowers, P. Eng., receives questions from members in need of advice and tips regarding the best practices to use when constructing raised patios. 

One of the most recent questions was related to a residential permeable interlocking concrete pavement (PICP) patio. Typically a PICP system uses a layer of ASTM #2 stone as the subbase, a 4 in. (100mm) layer of ASTM #57 stone above as the base and a 2 in. (50mm) layer of ASTM #8 stone on top as the bedding layer. Given this is a residential patio application, could the contractor only use a layer of #57 stone for the base or would it need to incorporate #2 stone as well?

The response, ASTM #2 stone provides better structural support for heavier, repetitive loads. It also tends to stay in place better than ASTM #57 stone, once it has been compacted. The drawback to using ASTM #2 stone is that it will typically require heavier compaction equipment and the need to manage another material on site. Given this project is a residential patio and will only experience light pedestrian loading, the ASTM #2 stone subbase is probably not necessary. It was also recommended that a highly permeable geotextile be placed between the ASTM #57 stone and the subgrade to improve separation between the open aggregate and the subgrade soil.

The system of ASTM #2 / #57 / #8 layers of aggregate are recommended because it has been demonstrated to work on numerous projects. However, an engineer familiar with the design of PICP systems may choose to utilize different aggregates.

Another question asked about the recommended installation best practices for a raised patio against brick veneer on a house? The response referred to the ICPI Advanced Residential Technician student manual.

When constructing a raised patio against an existing structure considerations should include: 1) creation of an air gap between the building’s exterior cladding and the raised fill using a retaining wall facing the building and 2) considering the additional load the raised patio will place on the foundation wall of the building.

Considering item 1, it is important to address water and moisture issues. It is important to ensure that rainfall landing on the patio surface is directed away from the house. Typically, a minimum grade of 1.5% is ideal to ensure that water flows across the surface. If the slope is lower than this, the water won’t move rapidly off of the patio. Slopes can be increased up to 4% to help speed the movement of water, but the pavement surface will be pitched. Tables and chairs will be on a noticeable slant, and the area can become a slipping hazard if ice forms on the patio surface. For larger patio areas, surface drains may be constructed to remove water from the surface. For smaller patios, it may be appropriate to have surface water flow across the patio, over the top of the retaining wall, and onto the garden or patio below. The use of stabilized joint sand may be appropriate to ensure that it is not removed by falling or flowing water.

Raised patio construction will likely affect the house. In most cases, there are two types of exterior walls: a) below grade foundation walls and b) above grade exterior walls. During construction, the compaction of fill places large dynamic loads on the adjacent walls. Placement of fill next to a building wall also increases the lateral load applied to the walls. The fill material used to construct the patio has moisture in it that can affect the building if the fill contacts the exterior walls. Below-grade foundation walls are typically constructed using concrete or concrete masonry units (CMU) waterproofed on the exterior with a drainage system incorporated at the base. Foundation walls are designed to withstand moisture against them continuously.

An above-grade exterior wall of a house can be constructed from materials such as wood, vinyl or aluminum siding, cement board, stucco, mortared clay, concrete brick, mortared stone or mortared veneers. These exterior wall materials are designed to support the load of the building above, and to resist the penetration of water. Placing compacted soil next to these types of siding can trap moisture in and against them, which leads to deterioration and eventually failure. Deterioration is accelerated when freeze-thaw conditions also exist. For raised patios with compacted fill material against the exterior wall, it is best to construct a stress relief wall leaving an air gap between the raised patio and the exterior wall. The stress relief wall can be constructed like any other segmental retaining wall on a raised patio project, but the face of the wall faces the exterior wall of the building. The air gap created needs to have drainage so any water that finds its way into the gap can drain out. It is also appropriate to encourage air circulation in the space to minimize condensation and allow the space to thoroughly dry out.

For item 2, when additional fill is placed adjacent to a building, lateral load applied to the foundation wall will increase. This is true even when a stress relief wall is used. For buildings with unbalanced fill conditions, like a basement, the weight of the additional fill can exceed the lateral strength of the foundation wall and can cause the wall to bulge and eventually blow out in to the basement area, potentially causing a collapse of the structure. Extra load is applied from the raised patio fill, but no extra resistance is provided by the foundation wall. Caution should be taken when taking on an unbalanced fill project, and an engineer should be consulted to ensure the stability of the project.

Image Above: Drawing from the ICPI Advanced Residential Installer Course manual.

Have an engineering or technical question? Robert is always ready to respond with the latest technical resources and information.

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Relaxing Traffic

David Smith, ICPI Technical Director

ICPI seeks partnerships to collect data, calm drivers and save lives

Just about every urban center in Canada and the U.S. is jammed with traffic, especially during morning and evening rush hour (or rush hours in bigger cities). Regardless of the city size, there consistently seems to be more cars and trucks than pavement to move them. It’s certainly not relaxing traffic for the drivers stuck in it.

Because they are just about the lowest density urban land use, residential areas don’t see many traffic jams. Thanks to spread out land use, residential traffic isn’t quite as hectic. While it’s not relaxing, at least it moves, even during rush hour.

Whether low or high density, residential areas are a rising source of complaints about near misses, car crashes, plus cyclist and pedestrian accidents. Vehicular traffic needs to relax, be calmed and be mindful of non-vehicular users.

There are a variety of tools and designs to calm traffic. They range from the ubiquitous (and cheap) stop sign to more visible designs that extend curbs to narrow intersections and slow traffic. Radical road remedies reduce flows and reclaim space for bus lanes, pedestrian refuge islands, bike lanes, sidewalks, bus shelters, parking or landscaping.

A main motivation for using calming remedies is creating safer streets. The benefits outweigh the costs. According to the National Safety Council, a car accident with an incapacitating injury costs the private and public sectors (medical care, loss of productivity, etc.) about $208,500. The direct and societal costs run over $4 million for each traffic death. In 2013, a motor vehicle injury occurred on average every 14 seconds according to the Rocky Mountain Insurance Information Association. Given these events and costs, an investment in traffic calming can be recovered almost immediately.

When it comes to using pavements to slow drivers, the options are limited: speed humps or the really annoying speed bumps. A forgotten form of relaxation is changing the surface to interlocking concrete pavement. A surface change means a visual and noise change that’s kinesthetically communicated to the driver via the steering wheel. Unfortunately, ICP doesn’t show up regularly in classic traffic-calming references published by the Federal Highway Administration, the American Association of State Highway and Transportation Officials, or the Institute for Traffic Engineers. Why? No experience and no hard before-and-after data.

So let’s start collecting data. The industry seeks a current condition where vehicular and pedestrian traffic conflict is a documented problem as measured by vehicle/pedestrian counts, near-miss reports, accidents and other incidents. For example, we are seeking conditions near schools where traffic calming is essential. We’d like to monitor before and after results via surveys and/or speed/traffic counters. We are seeking a partnership where other stakeholders participate with us financially as well as in the planning, execution and monitoring stages. Potential opportunities include school districts, police/fire/rescue stations, busy residential streets, libraries, parks, business districts and complete street projects. If there is traffic that needs calming, drivers that need to relax and slow down to spare injuries and deaths, we just might have a relaxing solution.

Image Above: Traffic calming Delbrück, Germany (called ‘traffic relaxing’ there) extends front yards into the street and narrows it while using pavers to slow drivers.

Image Above: Dutch traffic calming.

Interested in a partnership to make roads safer? Email icpi@icpi.org.