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The surface friction of an asphalt pavement is critical for ensuring adequate skid resistance and driver safety.

As virgin aggregates are costly and limited, recycled asphalt is often used as a base course in pavement construction. However, because the frictional properties of these recycled aggregates are unknown, it’s rarely used as a surface material.

To quickly assess the frictional properties of new and recycled aggregates and determine whether recycled aggregates could be used in cost-effective surface treatments, the Tennessee Department of Transportation conducted laboratory and field skid resistance measurement tests to identify practical devices and procedures for determining aggregate friction properties.

Read the report: Investigating the Long-term Frictional Properties and Establishing Aggregate Polishness Guidelines for Asphalt Surface Mixtures in Tennessee, April 2025.

Image source: Tennessee Department of Transportation

Truck-mounted attenuators (TMAs) are designed to protect workers in highway work zones by absorbing crashes, but drivers of these vehicles often face the most safety hazards.  

To improve safety for all workers, the Minnesota Department of Transportation initiated a research study to determine whether driverless TMAs could be a viable option for its fleet.

Read the project summary: Automated Truck Mounted Attenuators (ATMA), March 2025.

Image source: Minnesota Department of Transportation

In honor of National Work Zone Awareness Week, which takes place this week from April 21-25, we’ve rounded up a few of the innovative solutions that No Boundaries member states have recently shared to make working in and around traffic less hazardous for their highway maintenance crews.

• Automated Flagger Assistance Device. Missouri DOT field tested this device on a two-lane work zone and found that drivers behaved better than with a traditional flagger. Learn more.
• Night Light Safety Lighted Vests. Connecticut DOT’s maintenance workers wear rechargeable lighted vests when working in and around traffic at night to improve their visibility. Learn more.
• RAPTOR Temporary Rumble Strip Placer. Maryland DOT uses portable rumble strips to remind drivers to slow down in and around work zones. The RAPTOR vehicle attachment allows rumble strips to be placed and retrieved quickly and easily. Learn more.

Share your agency’s innovative products and ideas and explore others’ solutions on No Boundaries’ searchable Innovations Database.  

The March/April 2025 issue of Innovator, the bimonthly newsletter of the Federal Highway Administration (FHWA), highlights the efforts of several No Boundaries member states.

The California Department of Transportation (Caltrans) was noted for its contributions to the California Road Sharing (CaRS) program, a collaborative effort that establishes a framework for local agencies to integrate road data into Caltrans’ records to create a statewide dataset. 

Ohio Department of Transportation’s (DOT’s) Highway Safety Improvement Program was lauded for its work to reduce the risks of serious and fatal crashes by identifying areas where these types of crashes are most likely and prioritize projects that mitigate the risks.

Finally, South Carolina, Missouri and Colorado were all recognized for putting innovations into practice. South Carolina DOT has worked to increase public engagement by developing a virtual reality public hearing room and offering other opportunities for community members to participate in transportation-related discussions and decisions. The Missouri DOT has developed a crowdsourcing tool that leverages public input to identify pothole locations so they can be located and fixed quickly. And Colorado DOT’s use of innovative project delivery methods, including project bundling and design-build strategies, has allowed the agency to complete a bridge construction project in less time and for less cost than planned.

Sign up to get the next issue of Innovator delivered to your inbox.

Image source: FHWA

An asset management plan (AMP) can help transportation agencies keep track of maintenance needs and prioritize investments.

To support Indiana’s local transportation agencies and ensure they manage their transportation assets effectively, the State of Indiana passed a law in 2016 requiring each local transportation agency to develop an asset management plan as a condition of special funding.

To evaluate the agencies’ progress, the Indiana Department of Transportation launched a research study to survey the types of asset management plans that have been created.

Read the report: Assessing the Asset Management Programs of Locals: Bridges and Pavement Conditions, January 2025.

Image source: Indiana Department of Transportation