A smart motorway uses a number of systems working together in real-time to improve travel times, respond to emergencies and incidents and actively manage traffic based on the current conditions.
As opposed to a standard motorway which simply has a speed limit, smart motorways can have variable limits to improve driver safety and increase the amount of traffic that can travel. Lanes can be opened and closed as required, freeing up more capacity when needed, or restricting vehicles from a lane which contains a temporary danger.
The M4 in Sydney was the first to get a smart motorway system from Mays Hill to the foot of the Blue Mountains at Lapstone.
Ramp signalling is the main feature of a smart motorway and this helps traffic enter the motorway in a steady, controlled manner, improving merging on on-ramps. The time interval between green lights can be varied depending on the amount of traffic waiting to get onto the motorway, and the amount of traffic already on the motorway.
Variable message signs are used on the motorway and roads approaching the M4 to inform drivers about road conditions ahead. Lane use management can open and close lanes and change the speed limit according to the conditions, e.g. lower it in torrential rain.
A control centre monitors cameras along the motorway, and there are additional emergency telephones and stopping bays to help with safety when there’s a breakdown.
Advantages of smart motorways
Because they increase the throughput of traffic by maintaining higher average speeds, the advantages are:
- Less wear and tear on vehicles due to stop/start traffic
- More reliable travel times
- Less time spent on the road, which is good for business, reduces the amount of fuel used, and consequently reduces pollution
- Less frustration for motorists
- Safer travel when there are incidents
- Crash rates usually decline, up to 30%
- The cost of constructing and running them can be cheaper in the long run than the lost productivity of having standard motorways.