How driving slower could actually make traffic move faster

By August 30, 2018 Uncategorised

It seems counter-intuitive but there is building research that shows driving slower might help get motorists to their destination quicker in peak-hour conditions.

The theory comes from a Japanese engineer, who has said that leaving a constant gap of 40 metres could be the ‘Goldilocks margin’ to an ultimately free-flowing traffic network.

The University of Tokyo’s Professor Katsuhiro Nishinari studies the mathematics of traffic jams, a discipline he likes to call “jamology”.

“People are always trying to go fast. When they do, they tend to have less headway between them and the vehicle in front and that is very bad and is where traffic jams occur,” he said.

“A jam is a kind of wave in the opposite direction to the direction of travel. Waves is the propagation of braking but if there is headway, the next car does not have to break as much and these waves are dispersed between the cars.”

To put the theory to the test, Professor Nishinari headed to Tokyo’s Shuto Expressway – Japan’s busiest motorway – and the results reliably stacked up in the real world.

“At 4pm there was always about a 10km traffic jam. We asked eight cars to keep headway; we asked them to move more slowly than other cars and it was amazing. With just eight cars the jam didn’t appear for 40 minutes,” he said.

“If you continuously had all cars (keeping headway) maybe you can shift the onset again and have no traffic jam.”

Professor Nishinari’s views are not isolated, with Britain road bosses last year hatching a plan to cut the top speed of the MI motorway in Sheffield from 113km/h to 96km/h in a bid to ease traffic pollution and smooth the traffic flow.

“If you have an upper limit of 100km/h, some people will be doing 90km/h, so drivers will be slowing down to stop bumping into each other and there will be the temptation to change lanes which makes flows less efficient,” Professor Zoran Ristovski of Queensland University of Technology said

“If you have a lower speed you can stop all the shocks in the traffic flow and have a nice smooth flow.”

Will drivers want to slow down?

The biggest variable in all of this are the motorists themselves. Continued research has shown the majority of drivers deem low-level speeding acceptable and overestimate their own driver abilities. So such a move would require definitive action and a significant change in the way drivers engage with other vehicles.

The current industry standard safe-gap distance between cars is 2 seconds, but while travelling at 60km/h it would only provide a 34m gap between cars. Therefore aiming for a three-second gap might prove to be a useful measure to aim and ease congestion on our roads and get to that magic 40m mark.

The science definitely stacks up, so the only problem will be getting all Australian motorists on board with this somewhat counter-intuitive style of driving.

Good luck with that.