How TMAs Have Evolved to Meet Texas Road Safety Needs

Truck-mounted attenuators have changed a lot since the NCHRP 350 era. Here is what drove that change and why it matters for crews working Texas freeways.

A TMA is the shadow vehicle that parks behind a work crew and takes the hit when a driver drifts into the closure. The truck absorbs the impact and steers the errant vehicle away from the coffin corner near the cab. That job has not changed. What has changed is the crash science behind it, and Texas crews feel the difference on every mobile operation along I-35 and the Fort Worth loops.

From NCHRP 350 to MASH 2016

The older NCHRP 350 standard used lighter test vehicles that no longer match what actually drives on the road. MASH 2016 replaced it with heavier pickups and higher energy at impact. A TL-3 attenuator now has to survive a crash test near 62 mph. That single change forced manufacturers to redesign cartridges, mounting hardware, and the host truck itself.

• TL-2 units cover work zones posted at 45 mph or below.
• TL-3 units cover 50 mph and faster, including most Texas freeways.
• Every current unit needs an FHWA Hardware Eligibility Letter to be used on federal-aid projects.

Heavier trucks, smarter deployment

Modern host trucks run at roughly 26,000 lb GVWR or more so the truck stays put instead of rolling forward and letting the errant vehicle slide under it. Deployment also got faster and simpler. A crew can lower the attenuator into position in about 20 seconds, roll the unit at speeds up to 50 mph, and move the whole assembly to another truck in around 10 minutes when a job needs a different chassis.

Does a TL-2 unit work on a Texas freeway?

No. Freeways posted at 50 mph and above call for a TL-3 unit tested to the higher impact speed.

Do I need a new truck to upgrade the attenuator?

Not always. Many attenuators transfer between compatible chassis in about 10 minutes, but the host truck still has to meet the weight rating.