The most innovative of the three concepts submitted for the proposed Cambridgeshire Autonomous Metro is from Dromos. Its autonomous 4-seater pods are similar to those in use at Heathrow Airport. Could these be the future of urban and rural transport?
Dromos claims a capacity of 20,000 people/hour in each direction in the space of a normal road if they run at 30mph. By comparison, the theoretical capacity for cars is about 2,500 people/hour and, for buses, up to 90,000 people/hour.
But in the real world, vehicles have to stop to let people on and off, and give way at junctions. This reduces capacity drastically.
Dromos expects the throughput of an underground station with eight bays to be 800 people/hour in each direction. If the rate of arrival at the station in one direction exceeds that, queues of pods will form, which will also hold up people who are passing through. To avoid that you’d need to bore a second tunnel for through-traffic, doubling costs.
A busy stop like Cambridge railway station has thousands of people arriving and leaving in peak hours. Just one train can disgorge up to a thousand people. The bus station there, with four bays, can easily transport over 2,500 people/hour in each direction.
Two of the concept proposals argue strongly for running vehicles on the surface – to reduce costs and carbon emissions, and increase capacity, accessibility and resilience. But, autonomous operation in uncontrolled environments is still many years away. That means pods cannot run door-to-door, and would require segregated or elevated trackways to run at speed.
Are any of the concept proposals really better than running electric buses on existing roads? We have to deal with congestion of course. First, we need to build a comprehensive bus network. Then we need road pricing to incentivise people to use buses whenever possible, freeing up road space.
That will all cost far less – in money, time and carbon – than building the infrastructure for a completely new transport network. Where we do need high capacity and reliability, trams are the proven technology to deliver it.
This article was first published in the Cambridge Independent on 28 April 2021.