What is a Smart Motorway?
Smart motorway technology allows traffic flow to be actively managed, for example by imposing a temporary speed limit
A Smart Motorway is defined as a concept that utilises technologies and procedures to monitor and respond to fluctuating traffic conditions on our motorways. Smart Motorways which are being currently designed and installed have evolved from several years of feedback, lessons learnt and improvements since their first deployment on the M42 motorway in 2006.
How does a Smart Motorway work?
Smart Motorways function by adopting various operational regimes to meet scheme operational requirements including:
Variable Mandatory Speed Limits are applied to all types of Smart Motorways. A Mandatory Speed Restriction refers to the uses of a red ring speed restriction which is legally enforceable.
Traffic conditions are monitored using vehicle detection equipment installed in or adjacent to the motorway at strategic locations. The vehicle detection equipment is linked to a Motorway Incident Detection and Automatic Signalling (MIDAS) system which analyses the data and recognises two differing traffic conditions – Queuing Traffic or Congestion.
Queue Protection and Congestion Monitoring algorithms within the MIDAS system recognise differing traffic conditions and automatically set appropriate signs and mandatory speed restrictions on signals to actively manage traffic conditions. Safety specific intervention is provided by the Queue Protection algorithm which protects the back of queueing traffic and Congestion is managed by introducing reduced speed limits to increase traffic throughput.
In order to understand traffic conditions (such as speed and flow) the MIDAS system gathers traffic data from vehicle detector sites which are positioned at strategic points along the motorway network. There are two main types of detectors deployed within Smart Motorway schemes:
- Inductive Loops
- Radar Vehicle Detection
Variable Mandatory Speed Limit Enforcement
To ensure motorist compliance and to realise scheme operational benefits, Highways Agency Digital Enforcement Camera System (HADECS) equipment is installed within Smart Motorways. The latest cameras can monitor all lanes of traffic simultaneously and adjust the thresholds at which they capture offences to align with the varying speed restrictions.