Costs to outweigh benefits of increasing road speed limit
university-of-canterbury
Mon Jul 15 2013 12:00:00 GMT+1200 (New Zealand Standard Time)
Costs to outweigh benefits of increasing road speed limit
Monday, 15 July 2013, 12:05 pm
Press Release: University of Canterbury
Costs likely to outweigh benefits of increasing open road speed limit, UC expert says
July 15, 2013
Increasing the open road speed limit in New Zealand would have positive and negative effects, and it is important to assess and balance them thoroughly, a University of Canterbury expert says.
Associate Transport Minister Michael Woodhouse has not ruled out increasing the 100 kilometres per hour speed (kph) limit, and Police say they are open to discussion.
The main benefit effect is a reduction in travel times, as a result of increased speeds. However, "the travel time savings are commonly over-estimated", UC transport engineering professor Alan Nicholson says.
``This is because traffic speeds decrease as traffic density increases and many trips occur during peak periods, when traffic speeds are often less than the speed limit. Hence, the travel times for many trips will not decrease significantly.
``It is often argued that increasing the speed limit by 10kph will mean that drivers who currently travel up to 10kph over the current speed limit will no longer travel in excess of the speed limit. But this argument is flawed, as it incorrectly assumes no increase in traffic speeds after an increase in speed limits,’’ Professor Nicholson says.
``The main adverse effect is an increase in the frequency of accidents in which people are killed or seriously injured, and there is a tendency to under-estimate this effect. Another adverse effect is an increase in fuel consumption and greenhouse gas emissions.’’
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In October 2011, the UK Transport Secretary announced that the UK Government planned to launch a full public consultation on the issue of raising the motorway speed limit later that year, with a view to implementing any change in early 2013.
The UK Transport Secretary said advances in technology meant that cars were significantly safer than they were when the motorway speed limit was set, and that huge economic benefits could be created by shortening journey times. He also said that raising the limit meant that millions of otherwise law-abiding motorists would be brought back inside the boundary, restoring the moral legitimacy of the system.
``The same arguments are used by advocates of increased speed limits in New Zealand,’’ Professor Nicholson says.
The UK Department for Transport recently completed a thorough assessment of the impacts of raising the speed limit, taking account the full environmental, social and economic costs and benefits. This was followed by the UK Transport Secretary announcing earlier this month that plans to increase the speed limit on motorways had been shelved.
``It appears that the thorough impact assessment has found that the benefits of a speed limit increase are lower than previously estimated and the adverse effects are higher than previously estimated.
``I would expect a thorough impact assessment of an increase in the open road speed limit in New Zealand to also reveal that the costs will outweigh the benefits.’’
Professor Nicholson is presenting a paper at the World Conference on Transport Research Society at Rio de Janeiro this week. He is the New Zealand representative on the society which runs the conference.
ENDS
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