This document has been compiled to highlight and summarise road safety aspects related to roadworks, primarily in the United Kingdom. Research from outside of the UK is also included as and when necessary where it was felt that UK-based research was incomplete.
There are two main stakeholders in terms of safety at roadworks; these are the general public (predominantly road users) and the road workers. The safety of both these groups is achieved through the implementation of Temporary Traffic Management (TTM).
The key document regarding TTM is the Traffic Signs Manual (TSM) Chapter 8. This guidance document is the industry standard, and represents best practice for designing and operating TTM. The safety aim established by this document when setting up roadworks is:
“Underlying the design of temporary traffic management at road works should aim to produce a safety performance no worse than the rate for non-works conditions.”
TSM Chapter 8 goes on to set out the principles for TTM design:
- Provision of clear and early warning of obstructions in the highway;
- Optimisation of road space and the provision of an adequate safety zone and working space at works locations;
- Clear directions relating to decisions/actions required from road users;
- Minimisation of potential conflict between road users, and between road users and road workers and their operations;
- Credibility of traffic signs and temporary requirements; and,
- Speed limits and restrictions appropriate for the temporary highway geometry and safety features.
By following these principles and the guidance contained within TSM Chapter 8 (at a minimum) it is expected that the subsequent roadworks will be safe for purpose.
The following paragraphs summarise the findings of this synthesis relating to each of the principles stated in TSM Chapter 8:
Signing provides the ‘clear and early warning’ and gives ‘clear directions’. This synthesis has identified that setting out signs on high speed roads presents a particular challenge. Carriageway crossings are a high risk activity but are a common method of setting up signs for roadworks. Studies have examined driver comprehension and identified approaches to reduce carriageway crossing risk, by removing the need altogether or by making signs smaller and easier to carry.
Intelligent design of the roadworks layout optimises road space and provides the safe working space. The approach to road works and lane drops have been identified as areas of particularly high risk for conflict. One study in North America concluded that diversion of heavy vehicles away from the works zone was a particularly effective intervention. A semi-automatic cone laying machine trialled in the UK has shown potential to reduce road worker risk.
Barriers and a highly conspicuous workforce help to ‘reduce conflicts’ between road users and road workers. A Quick Moveable Barrier (QMB) has been successfully trialled in the UK; it gave the roadworks layout flexibility and reduced overall road worker risk exposure. Although road workers (and Traffic Officers) wear high visibility clothing, a study in the UK indicated that they typically over-estimated their conspicuity to drivers. This may induce complacency and increase safety risk.
‘Credibility of traffic signs’ has been found to be adversely affected when drivers perceive that road workers are not actually present. Similarly, an unpublished study showed poor understanding of and very poor compliance with advisory speed limits.
‘Speed limits and restrictions’ are widely acknowledged as a credible safety intervention. However, drivers must perceive that limits are enforced, otherwise compliance levels are low. Time over distance (average speed) cameras tend to produce a more stable speed reduction; spot speed enforcement is known to cause ‘surfing’ as drivers slow down only at the camera. Variable speed limits have been trialled both by simulation and on-road and have been shown to actually reduce speed variance (hence reducing RTI risk).
- Date Added: 03 Apr 2012, 08:09 AM
- Last Update: 30 Jan 2017, 12:33 PM