We did a series of vehicle travel time surveys in Brisbane CBD. Half of the trips were done by vehicles with drivers never going over 30kph. The other half were done travelling as an average vehicle.
The graph below shows a summary of the results. I will put further info on the experiment in a blog. In summary, the average vehicle was 3 minutes faster than the 30kph restricted vehicle and 2.4km/h faster.
Interestingly, all drivers involved in the surveys noted that they thought there would be little difference in travel times. Drivers also commented that the only issues with slowing to the <30km/h speed were impatient taxis. In my opinion, it is only a matter of time before the inner city 30km/h speed limits are introduced. The argument between travel time and safety lean towards the safety benefits.
Why 30km/hr is important.
Its all about road safety, especially for pedestrians and cyclists. The 2 main arguments for 30km/hr limits are:
1. Increased ability for car drivers to be aware of their environment
a. Better peripheral vision
b. Visual recognition between drivers and cyclists/pedestrians. At 30km/hr people can start to recognise that the other party knows that they are there.
2. Severity of crashes. The likelihood of severe injury or death decrease dramatically when vehicle speeds go below 30km/hr.
An interesting point is the movement to replace accident with crashes (or likewise). The theory being that crashes are preventable not accidents.