Smart Motorway features

The M4 Smart Motorway brings together a number of intelligent tools to help make your journey safer, quicker and more consistent. In order to navigate the new motorway, drivers need to be aware of the following signs and systems.

Traffic signs

Overhead gantries

These structures help to monitor traffic volumes and display different signs to help drivers navigate the road.

Traffic signs

Variable speed signs

Speed limits will change depending on the current traffic conditions. Although the speed limits will vary across the day, they are still enforceable.

More information about this technology is available in the M4SM Interactive Portal.

Traffic signs

Ramp signals

This is a quick change traffic light system for vehicles coming onto the motorway. During peak times, ramp signals will manage volumes of traffic coming onto the motorway making merging safer and ensuring the consistent flow of traffic.

More information about this technology is available in the M4SM Interactive Portal.

Traffic signVariable message signs

These are large, electronic signs situated on the motorway and in approaching roads. They will display information which informs drivers about expected travel times and traffic conditions.

More information about this technology is available in the M4SM Interactive Portal.

Variable lane use signs

These structures help to monitor traffic volumes and display different signs to help drivers navigate the road.

Traffic sign

Cross

A red cross indicates that drivers should not use this lane.

Traffic signs

Up left arrow

An arrow pointing up left indicates drivers should exit immediately at the next off-ramp. This is commonly used when there is an incident on the road ahead.

Traffic arrow

Down left arrow

An arrow pointing down left indicates drivers should merge left as soon as it is safe.

Traffic signs

Down right arrow

An arrow pointing down right indicates drivers should merge right as soon as it is safe.

Other features that work together to create the traffic management system include:

In-road traffic sensors

Road sensors every 500 meters and at entry ramps help to measure traffic volumes and detect traffic flow and speed changes.

Additional CCTV cameras

Over 100 extra live cameras on poles and bridges monitor real time traffic conditions to allow for quick responses to incidents.

Additional Maintenance Bays

There are extra bays and extra emergency telephones for vehicles stopping due to a break down or if an emergency stop is required.

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