What is ‘Inbound Flow Control’?

You will know that the City Deal has plans (“but no decisions have been made yet”) to build a busway from Cambourne to Cambridge, to add more bus lanes to Milton Road, and to build a bus lane on Histon Rd between King’s Hedges Rd and Gilbert Rd. The City Deal refers to these as ‘bus priority measures’.

Another such measure is a ‘bus gate’, which only (local) buses, taxis and cycles are permitted to pass through. In some places these block access for other vehicles (e.g. on Regent St in Cambridge). In other places (e.g. Newmarket Rd and Trumpington Rd) these ‘gates’ are combined with bus lanes to allow buses to overtake a queue of traffic. The benefit is often small, because traffic beyond the lights is moving slowly.

There is an enhanced version of this, which Smarter Cambridge Transport has termed ‘Inbound Flow Control’.

You may have experienced something called ‘ramp metering’. This is where rapidly cycling traffic lights on a motorway on-ramp release one or two cars at a time, ensuring the continued free flow of motorway traffic. Something similar could be done on Cambridge’s approach roads – as it has on Zurich’s: traffic lights about 500m in from a major junction (e.g. on the A14, M11 or A428) would release vehicles at a rate that ensures a smooth, uncongested flow into the city. An additional lane or two before the lights would contain the queue at peak times.

To give buses priority, you would then just need a 500m bus lane to the traffic lights, rather than all the way into the city. Beyond the lights, buses would flow with other traffic.

It might seem unfair to force people to queue on the edge of the city, but it turns out that journey times for most people would be the same or better than now.

We don’t need to destroy the character of residential roads and valued green space for bus lanes, which provide a small benefit for just a couple of hours a day. Inbound Flow Control offers a smarter, cheaper and more sustainable alternative.

This article was first published in the Cambridge Independent on 15 February 2017.