Changeable Message Signs for Road Safety and Traffic Management

A changeable message sign turns a static work zone into one that talks to drivers. Here is what a CMS does and how to use one well.

A changeable message sign, or CMS, displays text that a crew sets for the moment. Unlike a fixed sign, it can warn of a lane shift today and a full closure tomorrow. That flexibility is what makes it a core traffic-management tool for work zones that change day to day.

What a CMS communicates

• Advance warning of a merge or lane closure
• The reason for a slowdown, so drivers accept the delay
• Detour instructions when a route is closed
• Expected delay times to set driver expectations

Getting the message across

A CMS only helps if drivers can read it at speed. Keep messages short and place the sign far enough upstream that drivers have time to act. Pair it with an arrow board: the CMS explains what is happening, and the arrow board a few hundred feet later directs traffic out of the closed lane. Together they replace guesswork with clear instruction.

How is a CMS different from an arrow board?

An arrow board only points traffic in a direction. A CMS shows full text messages, so it can explain the reason, the distance, and the detour, not just the direction to move.

Can a message sign mount on a TMA truck?

Yes. We upfit trucks with mounted changeable message signs so one vehicle carries both the attenuator and the signaling for the zone.