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How wireless vehicle detection could give you the MIDAS...

How wireless vehicle detection could give you the MIDAS touch: a cost-effective alternative to inductive loops

In a bid to tackle congestion on England’s motorways,Highways England is working to maximise their capacity by making them ‘smart’. Smart motorway technology does this by optimising the flow of traffic in several ways.

A controlled motorway uses variable speed limits shown on overhead gantries to increase capacity. For example, reducing the speed limit to allow vehicles to travel closer together when traffic is building. Hard Shoulder Running schemes allow the hard shoulder to be opened during heavy traffic and All Lanes Running schemes keep the hard shoulder open to drivers, increasing capacity by 33%.

Each of these options to make a motorway smart rely on data regarding the traffic on the road, which is gathered using vehicle detection technology coupled with a MIDAS outstation. MIDAS (which stands for Motorway Incident Detection and Automatic Signalling) systems detect vehicles every 500m on the network to calculate volume, speed, and occupancy of each lane. Alerts for congestion and queuing traffic are created from this data using algorithms that calculate road occupancy levels.

In a MIDAS system, this data drives speed message signs downstream of the detected incident, so the signs reflect the situation on the road ahead and allow drivers to respond. For smart motorways, the same data is used to inform variable speed limits and open and shut lanes.

Clearview Intelligence supplied the vehicle detection equipment for the first use of MIDAS in the UK on the M25 ten years ago. This equipment relies on inductive loops connected to a MIDAS outstation. Inductive loops are a long-standing and reliable method for vehicle detection. However, loops can be challenging to maintain, especially should a fault occur with the loop furthest from the side of the road, which requires a long tail to reach the cabinet at the side of the road. This need to connect the loop in each carriageway to a control unit at the side of the motorway also means that the road must be shut completely while the installation is carried out.

Given the technological advancements that have taken place over the last ten years, it’s inevitable that newer technologies are now available to do the job of the inductive loop with two alternatives type approved to Highways England specification MCH1529 for use in MIDAS.

Radar sensors are one such approved technology. The radar is deployed at the side of the road, so this technology is easier to access for maintenance and can be installed without the complex traffic management required for the installation of inductive loops. Unlike loops, radar is also able to detect stationary objects such as debris in a carriageway.

However, these systems are significantly more expensive than loops, and with an average lifespan of 10 years, represent a regular outlay. Radar technology also struggles with very heavy congestion as the detection can fail to make out individual vehicles when they are very close together and slow-moving.

Wireless magnetometer sensors, such as Clearview’s M100 Wireless Vehicle Detection System, are the other approved alternative to inductive loops. The sensors are deployed in the centre of a traffic lane in one small (100mm x 50mm deep) hole and communicate wirelessly to an access point at the side of the road. The technology is quick to install and can be done one lane at a time. The sensors are placed in the centre of the carriageway, which means they can be installed at the same time as white lining is taking place, thus reducing road closures further.

Another benefit to the M100 system is that it can be installed in elevated sections of the network where the wearing course is thinner and can be damaged during the slot cutting required for inductive loops. It can also be utilised for ramp metering where vehicle detection on the slip road is combined with MIDAS information on the carriageway to manage traffic signals at the end of the slip road to regulate traffic flow onto the motorway.

Both radar and magnetometer systems offer reduced maintenance costs and can be installed more quickly and simply than inductive loops.

If you are resurfacing a section of your network or are looking to extend your vehicle detection ,get in touch to understand the cost and installation benefits of the M100 wireless vehicle detection system.
Uploaded 20/04/2017