Where did the Mill Road traffic go?

The Greater Cambridge Partnership installed fifteen automated counters to monitor traffic before, during and after the closure of Mill Road bridge. These state-of-the-art devices use image recognition software to pick out cars, vans, HGVs, cycles and pedestrians with high accuracy. What have they shown to date?

Averaging all the data available before and after the bridge closure appears to show about 1,200 motor vehicle trips/day ‘evaporate’ from the city end of Mill Road: only 3,800 of the 5,000 trip reduction can be found on Cherry Hinton Road, Coldhams Lane and Newmarket Road.

However, traffic reduces from the beginning of July anyway as private schools break up and people start going on holiday. The Big Weekend and Extinction Rebellion protest distorted figures for 5–7 July. If we exclude those dates and compare just two weeks’ data before and after the closure, the picture is somewhat different: the increase in traffic on diversionary routes almost exactly matches the reduction on Mill Road. The 7% increase in cycling matches the increase measured on Milton Road, so this may simply be seasonal variation.

It is difficult to draw firm conclusions even from a rich data set like this, but it seems not to provide evidence of traffic ‘evaporation’ or modal shift from cars to cycling. That isn’t surprising: extensive road works have made cycling along Mill Road much slower. It also takes time for people to adapt to new conditions.

On the east side of the bridge, residents, cafés and restaurants have benefited greatly from having more space for walking and sitting, reduced noise and cleaner air. This is to be celebrated. It can be a model for creating living streets – attractive destinations for shopping, leisure and socialising for residents, workers and visitors – here and elsewhere. Think Cherry Hinton Road or Mitcham’s Corner and that end of Milton Road.

Changes like this require dense networks of public transport and cycleways to make a car unnecessary for most trips into and around the city. This is essential to our zero carbon, zero pollution future, so let’s get on with it!

This article was first published in the Cambridge Independent on 14 August 2019.