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Just a few less school run car trips can eliminate congestion! Here's why..

Cars on street

When your roads are chockablock with traffic jams, reducing it can feel impossible. How do you get rid of thousands of car journeys? School holidays have shown us that it may not be as hard as it first appears.

In Dulwich, we see a huge reduction in congestion every school holiday and half term. Even when it is just the independent, non-catchment schools that are off (around 50% of pupils in the area), there is still a massive reduction. Why is that?

This graph shows Autumn Term 2021 data (from the TFL SCOOT traffic light sensor and control system) for Croxted Road, a residential A-road.

  • Most non-catchment schools in the area began half term on 18 October (the first black data point).

  • State catchment schools began half-term on 25 October (the second black data point).

  • All schools returned on Nov 1st.

This analysis shows there is notably less traffic (Vehicle Flow) and significantly fewer traffic jams (Congestion) in West Dulwich when non-catchment schools are on holiday. This reduces even more when the state catchment schools break up. We can see a reduction of just 100 cars at peak time can turn a London A road from bumper to bumper traffic, to light traffic flows.

vehicle flow graph

A tipping point

The graph shows us that the reduction in traffic (Vehicle Flow) is not as significant as the reduction in congestion, which means it takes just a few less cars to cause a dramatic reduction in traffic jams (Congestion). This is because once there is a certain volume of traffic, the tipping point is reached, which means traffic will slow to a crawl. Because school run car journeys all happen within the same short time frame, they push roads past their tipping point and generate bumper to bumper traffic. This analysis from TFL below clearly shows the extremely short timeframe all school run trips take place in.

trips by journey per hour graph

Such a huge surge in car trips all at the same time floods the road network past it's tipping point, which then creates traffic jams. This article here, provides a brilliant explanation of how just a few too many cars at the wrong time can make roads grind to a halt.

The Dulwich school run is a collective, identifiable body of cars that pushes the existing traffic levels over a tipping point to create congestion at peak times.

The good news!

Removing just 100 cars from our roads at peak times should have an obvious and beneficial effect. So let's get going! We have a list of solutions, on our Take Action page, from journey sharing to walking lines to school buses, that can enable more families to use sustainable travel for the school run. Rather than feel overwhelmed by the job of removing thousands of cars from our streets, we can do

something about it!


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