Don’t believe it, was the advice from these two transport specialists. Contrary to intuition, they explained, research conclusively shows that additional roads never reduce congestion for long. Adding road capacity creates “induced demand”; it encourages people to drive more than they otherwise would, to shop further from home, to live further from work, and to drive instead of using alternatives.
In some cases, adding a high capacity road can even make congestion worse because new roads encourage drivers to all converge on the same route, exacerbating the effect of bottlenecks. Beck said that studies consistently show that people spend similar time travelling wherever they live, about an hour a day, whether in Perth or Sydney or anywhere else. Adding more roads means more traffic, but not faster traffic. Traffic is like gas; it expands to fill the available space.
Alternatives to building more roads are using existing roads more efficiently; using techniques such as reversible lanes, where traffic travels in different directions at different times; congestion fees, such as the specific charges drivers pay to enter world cities like London and Singapore; and transit lanes. Transport research suggests, then, that the key question for cities like Sydney is not: “How do we fund the building of more roads?” but rather: “How do we optimise the road infrastructure we currently have?”
Moreover, traffic behaviour is set to change in the not-too-distant future. Our roads are not futureproof. One reason for this is technological: the advent of self-driving cars. Google, and others, have already trialled autonomous vehicles on public roads, achieving safety results better than human drivers.
The advantage of autonomous vehicles is that because they can be relied on to react faster than humans, they can travel closer together, allowing five to ten times as many vehicles to use the stretch of road as is possible with human drivers, with fewer accidents. It is also estimated that 25 per cent of congestion results from traffic accidents, of which 94 per cent are caused by human error.
The other reason for changes in traffic behaviour seems to be a generational shift that is under way, with fewer young people choosing to travel by car. These impending changes mean that the traffic models that transport planners use to forecast road usage in the future are unreliable. We know that behaviour will change, but even the experts cannot be sure by how much.
In response to questions, Beck and Bliemer said that we can only reduce demand for roads if we provide people with alternatives to driving, and that will only happen once enough people are prepared to act to make it happen. The two experts concluded by reminding the audience that, in the end, traffic planning is all about deciding what sort of city we want to live in.
