Making an intersection safe may involve signalisation – in normal language, we would say traffic lights. Traffic lights work but are expensive. The price is justified in the case of high traffic volumes or many accidents (Black Spot Program). For side streets, the simpler and cheaper way is zebra crossing.
Traffic calming is a way of making roads safer for people – people on bikes and people who are walking. The roads have been traditionally laid out for cars. The logic is that money is time and the roads should be efficient so cars can get there quickly. This approach does not work. As the traffic jams around the world have demonstrated, we do not get there quickly – often riding a bike or public transport would be faster. Driving is for many people just a habit.
You may have heard of the term modes of transport. This recognises the other ways to get around rather than drive. The most common forms are public transport, cycling and walking. The percentage of people doing each is called mode share. In some cities, such as Melbourne, the mode share of public transport, cycling and walking is quite high.
The percentage of people using a particular mode of transport; the ACT has targets to achieve a mode share of 7% by walking, 7% by cycling and 16% by public transport of all journey to work trips by 2026. “Building an Integrated Transport Network: Active Travel (ACT Government, May 2015)
The idea of traffic calming is that we should build our transport infrastructure for all modes of transport. Traffic calming is where we redesign the roads to encourage cycling and walking by making the cars a little slower and encouraging drivers to consider alternate routes.
High speed intersections
Roads with high speed limits have wide corners, wide lanes and wide intersections with good sight lines. Further, the corners are designed to permit cars to turn at higher speeds. The logic: slowing a car cause congestion that interrupts the traffic behind it.
So much for the theory. The problem with high speed intersections is that our vision narrows at speed. We see less of what is left and right of us. This is in part due to the brain’s limited processing speed. If we drive faster, our brain does not work faster. To avoid overloading, our brain simply throws away all the unimportant stuff happening on the edge of our vision. This is an unconscious process so that we are unaware of the effect and unaware of what impact it is having on our decision-making.
Information box: cognitive biases
Reference: Thinking, Fast and Slow by Daniel Kahneman
The cognitive bias is called what-you-see-is-all-there-is. This means quite simple that the automatic process (heuristic) or fast thinking that is dominated when driving is blind to omission – what is not there. Making the problem worse still is that or fast thinking is not capable of conceiving all the things we do not know. The conscious part of our mind – slow thinking – can do that. It can pose the question, “Is there anybody on the side road trying to cross here?” Our slow thinking comes with a price, it tires quickly and using it requires our continual focus – and that takes effort. It is easy to inattentive – a common cause of traffic collisions.
The limitations of our brain, and drivers general ignorance that they have them, is very unfortunate for people on bikes and people who are walking, as drivers simply do not notice that they are there. A driver may turn into the side roads at speeds higher than the speed limit and not notice that they almost ran down a person crossing the road.
The idea behind traffic calming is to slow down the car BEFORE it enters the side street. The drive has then the time to notice the people on bikes and people who are walking that wish to cross the road and can stop before colliding with them. This is the essence of a forgiving Safe System. Drivers will make mistakes, but the roads should be design so that the consequence of those errors is not fatal.
The intersection of Theodore Street with Melrose Drive was redesigned because the high speed design was unsafe. Theodore Street is a 60 km/h zone and the Melrose Drive much faster. Cars were “speeding” through the corner – an error caused in part by its bad design!
How the corner was improved:
- The corner has now a tighter radius, so the cars must travel at a slower speed to take the turn.
- The lighting is much brighter so that people on bikes and people who are walking can be seen.
- A pedestrian crossing reminds the driver that they must give way to people on bikes and people who are walking.
- The pedestrian crossing was raised on a platform – a zebra crossing. The vertical deflection slows the cars further.
Zebra crossings are great as they greatly improve the safety of people on bikes and people who are walking and prioritise these modes of transport. Zebra crossings are an example of a treatment recommended by Austroads for vulnerable road users as part of the Safe System approach. Good road design really does make it much safer for us to get around on foot or by riding a bike. 🙂