At What Speed Do You Need a TMA?

What is a TMA?

A Truck-Mounted Attenuator (TMA) is a safety device. It goes on the back of a truck. The TMA helps keep people safe. When cars hit the TMA, it slows them down. This makes crashes less bad.

TMAs save lives. They stop cars from hitting workers. They work in work zones. They help on roads where cars go fast.

Why Speed Matters for TMA Use

Speed is a big deal for TMAs. The faster cars go, the more you need a TMA. Let’s look at when you must use a TMA based on how fast cars go.

Key Speed Rules for TMAs

Here’s when you need to use a TMA:

• When speed limits are 60 km/h or more during setup work
• When regular speed is 80 km/h or higher
• In the US, when speed is 45 mph (72 km/h) or more on roads with 4+ lanes

Speed matters a lot! Fast cars need more time to stop. TMAs help when stops are quick.

Speed Rules by Place

Rules for TMAs are not the same in all places. Here’s what you need to know:

Australia TMA Rules

In Australia:

• TMAs must be used when speed is over 60 km/h
• For long work, they put up lower speed signs
• TMAs show speed limits on signs

United States TMA Rules

In the US:

• Virginia needs TMAs on shadow cars when speed is 45+ mph
• Illinois has new TMA rules for 2025
• TMAs must be used for all mobile work in some states

When Do You Need a TMA? A Simple Guide

Let’s make this easy to get. Here’s a simple table:

Speed	Do You Need a TMA?	Notes
Under 60 km/h (37 mph)	Maybe Not	Check your local rules
60-80 km/h (37-50 mph)	Yes	Needed during setup and pack up
Over 80 km/h (50 mph)	Yes	Must have TMA for all work
45 mph+ in US (4+ lanes)	Yes	Required on shadow vehicles

TMA Use in Real Work Zones

TMAs are used in many types of work:

• Highway paving work needs TMAs
• Material testing crews use TMAs to stay safe
• Night work zones need TMAs even with lower speed limits
• Mobile work like road line painting needs TMAs

A Crash Attenuator Safety Truck is vital for work zones with high speeds. These trucks have special gear to keep workers safe.

TMA Speed Rules – Research Findings

Research shows why TMAs matter:

• Speed limit increases led to 5% more crashes in one study
• TMA vehicle speed affects how cars merge around work zones
• TMAs work best when they match the speed of traffic

Special TMA Uses

TMAs aren’t just for regular road work:

• Setting up work zones needs TMAs
• Ending work zones needs TMAs too
• Mobile operations always need TMAs in some states

For larger projects, Road Maintenance Vehicles for Highways often come with TMAs built in.

Future TMA Rules for 2025

New rules are coming soon:

• Illinois will have new TMA rules in March 2025
• More signs will be needed when speed drops by more than 10 mph
• Speed limiters may affect how TMAs are used

Best Ways to Use TMAs

To use TMAs the right way:

1. Check your speed zone first
2. Place TMAs between workers and traffic
3. Show the right speed limit on TMA signs
4. Use TMAs in convoys for mobile work
5. Keep TMAs visible to all drivers

Street Maintenance Vehicles often use TMAs to protect workers during road repairs.

TMA Safety Tips

To be even safer with TMAs:

• Put up good signs before the TMA
• Use bright colors on the TMA
• Make sure the TMA is the right size for the speed
• Keep the TMA at the right distance from workers
• Check that the TMA works right every day

Common Questions About TMAs

Stay Safe with TMAs

TMAs save lives. They keep workers safe. They help when cars go fast. Know the speed rules for TMAs in your area.

Remember:

• 60 km/h – You may need a TMA
• 80 km/h – You must have a TMA
• 45 mph – US roads with 4+ lanes need TMAs

Use the right TMA for your job. Keep it in good shape. Follow all the rules.

Want to learn more about work zone safety? Check out our guide on Emergency Power Trucks that often work with TMA vehicles.