You need to watch out for ‘phantom traffic jams’
Traffic at a standstill
Millions of people will take to the roads this weekend only to end up spending hours sitting in traffic jams. The RAC estimates that 14.1 million motorists will make journeys for holidays or day trips between Friday and Sunday, the second highest since it began tracking the data in 2016.
Most schools in England and Wales have broken up for the summer holidays this week or will do so early next week, while the academic year has already ended in Scotland and Northern Ireland. The RAC predicted Saturday will be the busiest day on the roads for getaway journeys, with 3.8 million planned, while Friday and Sunday will each see an estimated 3.4 million.
The Port of Dover expects to have about 7,500 outbound cars on Friday, rising to nearly 10,000 on Saturday, as the RAC warned that south-west and north-west England are likely to see the most leisure traffic.
An expert has explained whether you are better off or not switching lanes in a bid to cut your journey time on busy roads. Randa Herzallah, Associate Professor of Applied Mathematics, at the University of Warwick, said: “If you’ve ever found yourself staring enviously at the lane next to you, convinced it’s moving faster, you’re not alone. Most of us instinctively believe that changing lanes will get us home sooner. But mathematics suggests this intuition is usually wrong.”
Professor Herzallah said many queues you will come across this weekend are ‘phantom traffic jams’ – stop-start waves that travel backwards through traffic even though every vehicle is moving forwards.
She added: “There is an optimal traffic density that maximises the number of vehicles passing through the road each hour. Beyond that point, adding more cars reduces the efficiency of the road – and increases the time it takes everyone to get to their destination.
“The same mathematics explains why constantly changing lanes is rarely worthwhile. A lane change creates a small disturbance that neighbouring drivers must react to. If many drivers behave in the same way, these disturbances accumulate and increase the likelihood of traffic waves. So, what feels like a clever decision for one driver can ultimately make conditions worse for everyone.”
Professor Herzallah said there are three driving tips backed up by strong mathematical evidence, and if everyone adopts them, it should reduce the time you spend in traffic queues.
- Maintain a safe following distance;
- Accelerate and brake smoothly;
- Resist the temptation to keep switching lanes in search of tiny gains.
She told The Conversation: “Applied mathematics shows the fastest way to your destination isn’t to drive more aggressively. It’s to help keep the entire system stable.”
