Speed Limits and Travel Times

Speed limits around our city and our suburb are lowering in busy places or where safety is an issue (eg outside rest homes and schools).    

I have had quite a few conversations recently about how speed limits affect travel times.  Many people that I talk to think that if the speed limit drops from 60km/hr to 30 km per hour around town that travel times will double.   I must admit that if I’m in a hurry, it sometimes  feels like that is the case, but the reality is actually quite different.  Knowing this helps me to be more patient.

 

We often don’t travel at 50km/hr round town even when that is the speed limit, particularly in busy areas.    In rush hour, for example,  the sheer number of cars mean that we are not travelling very quickly and traffic speeds into the city are seldom much more than 30km/hour and often much less than 20km/hr (and we see this as people on bicycles go sailing past us).

This NZ Transport Agency report  shows that driving at a slower speed usually results in a relatively small increase in travel time, particularly when travelling around the city.   Factors, such as lights, traffic, and intersections have a much greater effect on our travel time.  No matter what, even out here in Halswell, we have to stop at traffic lights and intersections, slow down near schools and go slow for any road works.

Some figures from the NZTA report: 

·         Reducing the maximum speed from 100km/h to 80km/h on trip from Christchurch to Kaikoura (tested 42 times by different drivers) showed an overall increase in travel time of 12 minutes.

·         For trips round Wellington reducing the maximum speed 25% from 50km/h to 40km/h showed travel time increases ranged from 1-2 minutes over a 6-10 km trip.

These extra times seem a fairly small price to pay for fewer injuries and deaths from crashes.  In Christchurch, as in other centres, where 30km per hour limits have been used in busy areas, crash rates and injury rates have dropped significantly.