20mph limits help people to reach their destination quicker

People wrongly assume that 20mph limits delay journey times. Yet, average city speeds are generally well below 20mph owing to congestion and queues. And traffic flows more freely at 20mph than 30mph: drivers make better use of road space by packing closer and junctions work more efficiently and at a higher capacity as its easier to merge. Because drivers feel safer, some leave their cars at home, further reducing congestion. 20mph limits mean quicker journeys.

Optimal speeds for maximum urban traffic flow have been mathematically modelled and 20mph is more efficient than 30mph.

· Drivers cut their spacing as braking distances contract. Shorter gaps mean more vehicles can use the available road space, reducing standing traffic.
· Filtering at junctions becomes easier too. It is far easier for motorists to pull into traffic travelling at 20mph than at 30mph. So junctions work more efficiently and queues reduce.
· Motor traffic volumes decrease since slower speeds encourage active, sustainable and shared travel. Walking and cycling levels rose by up to 12% after Bristol’s 20mph limit
· Buses operate more efficiently. The reduced length of queues means that bus journey times decrease, and become more reliable. Buses become a more attractive alternative to the car.

For more information visit http://www.20splentyforus.org.uk/BriefingSheets/20mph_Improves_Traffic_Flow.pdf