In this article, Civil Engineer Thomas Lyden and Automotive Engineer Roland Hoover provide an overview of pavement crack sealing and discuss how misapplications of sealant can contribute to motorcycle and bicycle crashes.
Pavement Crack Sealant & Motorcycle Crashes - Expert Article
Sealing roadway surface cracks with tar and other sealant materials is a common maintenance practice intended to prevent water intrusion and further pavement degradation. However, if not properly performed, this practice can negatively affect roadway friction and create surface irregularities; both of which can contribute to the cause of motorcycle and bicycle crashes.
Hazards to Motorcyclists & Bicyclists
Roadway repairs to address pavement degradation, surface cracks, and irregularities have the potential to negatively affect vehicle control and must be performed in a manner that considers the driving dynamics of all road-going vehicles, including motorcycles and bicycles. Crack sealing activities are no exception, and the transportation and construction industries are well aware of the associated hazards .
The materials used for crack sealing tend to be very slick when wet or oily. A reduction in the coefficient of friction between the roadway surface and the tire contact patch can be especially dangerous for 2 wheeled vehicles. With the contact patch of a motorcycle at about the size of a tennis ball and a bicycle’s as small as a dime, these vehicles are frequently operated with the entirety of their tire contact patch upon roadway repairs. Unlike passenger cars and trucks which distribute their weight across four tires in total, and at least two at each axle, and are generally unaffected by the loss of traction in a single tire, the stability of balanced vehicles is significantly compromised where either tire encounters slick conditions.
Beyond slick conditions, road repairs that cause a bump or ridge in the direction of travel can lead to an unintended steering effect or a lack of steering response, creating a loss of directional control.
Frictional changes or unintentional direction changes while riding a motorcycle or bicycle are the cause of many single vehicle crashes.
Proper Application of Crack Sealant
Crack sealing is not an appropriate solution for all surface defects and must only be applied to pavement distresses which will benefit from its timely application. As previously noted, the misapplication of sealant is not only wasteful; it has the potential to create hazardous surface conditions.
Issues to Watch For in Crack Sealing Cases
- Contract Terms – It is important for municipalities to establish contract terms that promote best practices. Paying by the pound of sealant material applied invites overuse of material which could lead to slick conditions.
- Seasonality of Repairs – Sealant applied to cracks during colder months may be forced out of the crack as the pavement expands during warmer months creating bumps in the road surface.
- Means & Methods – Materials and techniques should be specified with safety in mind. Some techniques, are chosen because they are quick and easy, but if performed improperly can result in irregular surface conditions.
- One example is overbanding, which is easy to apply and does not require the use of a squeegee to remove excess sealant. This can allow for up to 5 inches of excess sealant to remain on the pavement surface, and a “cap” of ¼ in material may remain, creating a bump.
- Pavement Markings – Applying crack sealing material over existing pavement markings obliterates these markings rendering them inadequate for their intended use of safely guiding motorists.
- Material Tracking – Sealant can stick to tires and be pulled out of the crack. Sand, limestone dust, or even toilet paper can be applied as a blotter to prevent tracking of the material.
Guidelines for Safe Crack Sealing
In order to improve safety, there are a number of standards and industry practices guiding the use of crack sealant.
- Evaluate the existing pavement and assess the density and general condition of the cracks. In some situations, crack sealing may not be the proper maintenance strategy and may create additional hazards.
- Train personnel in application methods and work zone safety procedures.
- Establish proper traffic control for the work zone.
- Inspect and calibrate the application equipment.
- Follow the manufacturer’s recommendations for storage, handling, and placement of the material
- Sample and test the sealant material.
- Conduct end-of-the-day and end-of-the-project inspections.
- Re-establish any obliterated pavement markings.
- Periodically evaluate the pavement for bumps and slick conditions.
Road maintenance personnel must be trained on motorcycle and bicycle safety issues with any maintenance practice, but especially crack sealing operations.
HIGHWAY ENGINEERING INVESTIGATIONS
The highway experts at Robson Forensic examine crash sites, use field measurements, scrutinize crash scene photos, and review infrastructure design documents to determine if highway factors or road conditions contributed to the cause of motor vehicle crashes.
The specific actions of a bicyclist within the context of an incident will often be evaluated by a specially qualified bicycle expert. For more information on bicycle experts at Robson Forensic, please visit our Bicycle Forensics page.
For more information contact the authors of this article or submit an inquiry through our website.
Thomas Lyden, P.E., PMP
Civil Engineer & Highway Engineering Expert
Thomas Lyden is a civil engineer with an impressive background covering the entire lifecycle of highway infrastructure. Prior to joining Robson Forensic, he was employed for 31 years by the Ohio Department of Transportation. Throughout his tenure as an ODOT employee, Thomas held various positions involving traffic engineering, maintenance operations, transportation planning, and project management. In his later roles with the Department of Transportation, Thomas established the training programs for winter roadway management, developed maintenance standards and oversaw routine maintenance activities involving pavement condition, guardrails, signs, pavement markings, and pavement drop-offs. Thomas is licensed as a Professional Engineer in multiple states.
Automotive Engineer & Motorcycle Expert
Roland Hoover is a mechanical engineer with broad experience in automotive and motorcycle engineering. His career includes more than 20 years of engineering experience at OEM vehicle manufacturers, aftermarket parts manufacturers, racing teams, and specialty performance tuners.
Prior to joining Robson Forensic, Roland was a Research & Development Engineering Manager at an aftermarket motorcycle parts manufacturer; in this role, he was responsible for the development and testing of wheels, drivetrain, steering, braking, suspension, and electronic systems components. In addition to new product development, Roland was also responsible for root cause and finite element analysis investigations into product failures and consumer complaints.
- NCHRP Project 20-68A, Scan Team Report: “Leading Practices for Motorcyclist Safety”
- NCHRP Report 784 “Best Practices for Crack Treatments for Asphalt Pavements”
- FHWA Report RD-99-147 “Materials and Procedures for Sealing and Filling Cracks in Asphalt-Surfaced Pavements”
- US DOT National Highway Traffic Safety Administration: National Agenda for Motorcycle Safety, Roadway Characteristics.