When the first roundabout in the UK was built in 1909, there were no rules about how to use it! As traffic flow increased, queues quickly built up, blocking exits and locking the entire roundabout and surrounding roads. TRL’s later research found how to make roundabouts work effectively, using advisory give way signs and priority rules. These were introduced by 1956, allowing widespread use of roundabouts to keep traffic flowing in the UK.
Traffic signal control
Traffic lights help traffic flow smoothly and make it safer for pedestrians and cyclists to cross roads. Our research into real time adaptive traffic control systems began in the early 1970s. We analysed traffic data for a range of scenarios and times of day to create optimal signal plans. We captured them on a computer model which monitored traffic flows over the whole network. This allows adjustments to signal timings to minimise traffic delays.
SCOOT (Split Cycle Offset Optimisation Technique) coordinates the operation of all traffic signals in an area to help vehicles progress through it steadily. SCOOT is used in 250 towns and cities worldwide, reducing emissions and congestion. It reduces journey times by an estimated average of 12%.
In the 1970s, there was more congestion and therefore a higher risk of collisions on rural A and B roads. We studied accident risks related to junction design and recommended using traffic islands and give way signs. These forced drivers to stop and give way to other drivers, whilst keeping a steady flow of traffic. After four years we saw a 50% reduction in accidents.
Driverless vehicles are set to become a part of the future transport landscape. To contribute to their safe evolution, we partnered in a project to understand how to navigate driverless vehicles safely on the road network. We examined vehicle-to-everything (V2X) communication and how to gather and use data in urban planning to support deployment of automated transport systems. Our project found that present and foreseeable communications bandwidth isn’t enough to allow complete mapping data to be reliably streamed to vehicles. We recommended that in the short term, vehicle manufactures will need to provide as much mapping data in cars as possible.
To improve driver and passenger experience through roadworks, we reviewed speed management approaches on behalf of Highways England. Trials in our driving simulator and on live roads helped us understand the impact of increasing speed limits through roadworks from 50mph to 60mph. We found that major schemes can maintain safety with the higher speed restriction. Our ongoing work examines whether this approach can be extended other kinds of roadworks.Highways England is investing heavily in “smart motorways” thanks to years of research by TRL into the application of innovative traffic control technology and electronic signage. Flexible use of lanes provides extra capacity at peak times. Controlling traffic flow from Highways England regional control centres makes journeys more predictable and timely for all road users.
Links to projects or case studies
- Junction design or signs reports
- Parking reports
- Reducing congestion at roadworks