Road space utilisation improves travel times, reduces costs

For major road works schemes, necessary lane closures are timed to minimise congestion, most frequently at night and on weekends when traffic is at its lightest. As a result, rigid timetables are used in planning, programming and implementing work.

In the UK, to calculate the expected traffic demand through roads works, historic profiles from the loop-based MIDAS (Motorway Incident Detection Automatic Signalling) system were used. These provided a valuable indicator of anticipated traffic behaviour but were limited as they are only a prediction based on historical experience.

To overcome this limitation and to improve the accuracy of the MIDAS system, 491 TRL, in collaboration wth 2002 Costain and MTS (2003 Mobile Traffic Solutions) developed DRUM (Dynamic Roadspace Utilisation Manager), a traffic management system for road works based on real-time traffic information. This allows for lane closures to begin earlier and finish later, when the conditions are right.
It maximises the time available for lane closures and increases carriageway capacity through road works which has implications for journey time reliability as well as environmental benefits derived from fewer traffic queues and thus CO2 emissions.
Project:
• Dynamic lane closures during roadworks
Cost:
• US$75,000
ROI:
• US$385,000
Benefits:
• Allows contractors to work more flexibly, efficiently, and cost effectively
• Improved journey time reliability
• Reduced queuing
• Reduced CO2 emissions
In 2008, DRUM's use on the M25 (Dartford Widening Scheme) and M27 (J11-J12) allowed road works to be completed some 25 per cent faster when compared to roadworks programmed and implemented using traditional methods. This gave a cost benefit return of a minimum of 4.5 times its deployment cost.

How it works

To improve the accuracy of the MIDAS system, it was recognised that the strength of the prediction model could dramatically be enhanced by comparing predicted flow levels with the real-time flow.

To collect this data, TRL teamed up with MTS using its T-25, a mobile power source trailer with an 8m telescopic mast. An environmentally friendly solar-recharged system, the T-25 is suitable for multiple applications including traffic counting, CCTV and ANPR.

Mounted on the telescopic mast is a 148 Wavetronix SmartSensor HD non-intrusive side-fired microwave radar. This effective live tool provides a 10-lane dual-directional capability with over 96 per cent of accuracy, capturing live data from within the road works. A selflearning algorithm constantly corrects for the effects on flow of the road works themselves, such as commuters altering their routes to avoid the road works, and over time becomes increasingly accurate.

The system architecture turns the collected data into a useable tool which provides a dynamic timetable of optimal closure times. Traffic and planning managers are then able to view this information via a Webenabled PDA or standard PC with internet connection. Access to this dynamic information removes the limitations of restricting road works' closures to set times, which are costly to the highways industry in terms of missed opportunities and less effective programme management.

M61 experience

Last year, DRUM was deployed on the M61 motorway improvements scheme between Junctions 3 and 4.

Prior to this, lane closures were undertaken in accordance with a Lane Prohibition Plan (LPP) to minimise congestion resulting from lane closures.

To quantify the benefits arising from DRUM's deployment, a simple comparison was undertaken by recording actual working times against those that would have been available if working in accordance with the LPP.

DRUM was fully operational between the end of May 2009 and the second week in September 2009, and a record was made during each shift for each carriageway. This record detailed when DRUM indicated lane closures could be implemented, when the LPP would have allowed lane closures, and the actual hours lane closures were installed.

The data revealed that DRUM provided opportunities to work extra and longer shifts than would have been permitted by the LPP, particularly in the evenings and during the day at weekends. The latter proved to be a major benefit to the scheme, allowing closures to remain in place throughout each weekend. This enabled extra shifts to be put on and works which benefited from continuous shifts or daytime working to be programmed for completion at a weekend.

Analysis of the records revealed a US$385,000 saving provided by DRUM as against the LLP, which was achieved through enabling the contractor to work more flexibly, efficiently and cost-effectively.