TRL has worked with the Highways Agency on three options for managed motorways, from their initial conception and development to implementation. The options are Controlled Motorways, Active Traffic Management and, more recently, Basic Controlled Motorways.
TRL was involved from the beginning in the design of the M25 (J10-16) Controlled Motorway, primarily determining the variable speed limit (VSL)-setting algorithm and the thresholds and operational tuning through an intensive period during initial operation to ensure its behaviour was valid for the traffic.
We provide support to the operational maintenance of the system both directly for the Highways Agency and now via the new South East Region Traffic Technology Managing Agent Contract to ensure that it's operating effectively.
The support includes:
- development and implementation of the Motorway Incident Detection and Automatic Signalling (MIDAS) loops 'Health Check' process, providing weekly reports on the condition of all the enabled MIDAS sites within the region
- identification of MIDAS sites generating spurious high-occupancy (HIOCC) alerts
- provision of expert advice and analysis to the Highways Agency Information Line (HAIL), particularly for queries regarding the M25 Controlled Motorway scheme
- design and management of the MIDAS maintenance database, an online fault-reporting system to facilitate the upkeep of MIDAS through a central database for all stakeholders.
Benefits of the M25 (J10-16) Controlled Motorway are now widely accepted by stakeholders, including road users.
Active Traffic Management
We supported the Highways Agency during concept development of the M42 (J3a-7) Active Traffic Management pilot scheme and undertook the following tasks:
- aiding the site selection process by assessment of traffic conditions at potential pilot sites
- development of generic operational regimes (ORs) and those likely to be suitable for the M42 pilot scheme
- detailed assessment of traffic conditions on and around the M42 pilot site, prior to implementation of Active Traffic Management.
We've also undertaken the following tasks for Mouchel, the lead managing consultant, during the scheme implementation:
- developing the signal thresholds for three-lane and four-lane VSLs
- assisting with the operational tuning of the scheme, including the development of a new technique (adapted from Controlled Motorways 40 mph settings) for smoothing the signal settings to counter the highly variable speed settings possible with Active Traffic Management which can cause concern for drivers
- reviewing the use of the link flow state boxes for providing guidance to the operators on when to open and close the hard shoulder
- investigating the potential operational impact of increasing the speed limit during hard shoulder running from 50 to 60 mph
- currently, determining the thresholds for the Birmingham Box Active Traffic Management rollout undertaking from Mouchel.
The M42 scheme is widely appreciated by stakeholders, including road users. Some statistics published on 30 June 2008 by the Highways Agency in their document 'ATM Monitoring and Evaluation - 4-Lane Variable Mandatory Speed Limits - 12 Month Report (Primary and Secondary Indicators)' are as follows:
- in 2007 (four-lane variable mandatory speed limit (4L-VMSL)), 30% of long-distance users thought the M42 was better or much better than other UK motorways, compared with 16% in 2003 (no VSL (NO-VSL)). This shows a marked improvement in perceptions of the M42 among long-distance users
- on average 13% more local users and 27% more long-distance users perceived that it was easier to join, change lanes and exit the M42 in 2007 (4L-VMSL) compared with 2003 (NO-VSL)
- the understanding of both local users and long-distance users in terms of the purpose of Emergency Refuge Areas (ERAs) is very high (more than 95%)
- the results showed that users perceived lower levels of congestion on the M42 Active Traffic Management section between 4L-VMSL (46%) and NO-VSL (39%) (an extra 7% of users encountered no congestion). This enables users to predict their journey time more reliably. This is supported by the journey time and flow/speed analysis.
Basic Controlled Motorways
A third option for managed motorways is Basic Controlled Motorways which is at the stage of completed concept development. This is a cost-effective solution which aims to make use of existing MIDAS infrastructure coupled with Message Sign Mark 4 signs and requiring few gantries.
The concept was developed with Mouchel for the Highways Agency and is now part of the Route 21 strategy. It has the following benefits:
- reduced complexity
- retains the key benefits of Controlled Motorways
- designed for D2/D3 Motorways or D2/D3 all-purpose trunk roads
- can be ‘bolted-on' to existing MS3/4 infrastructure
- cost-effective - provides key benefits of Controlled Motorways at minimal cost.
If you're interested in learning more about the topics covered in this section, or you can't find what you're looking for and would like to talk to someone in detail about this topic, please email Trafficoperations@trl.co.uk