The government is wanting to increase motorway speeds from 70mph (112km/h) to 80 mph (130 km/h). The Transport Secretary explains: “We need to do this on a pretty rigorous cost-benefit analysis basis…at the moment there are a clear set of criteria for making these decisions. Perhaps we ought to ask if we are using the right set of criteria”.
Netherlands is also planing to increase it’s motorway speed limit to 130 km/h while Spain is currently lowering its speed limit from 120 km/h to 11o km/h to reduce fuel imports! Check out this useful blog post on the subject confusion that we are in at present.
Lets do a rough and ready cost-benefit analysis given that both the ‘costs’ (ie mainly injuries, deaths) and the benefits (mainly a few minutes off journey time for car drivers) can be reasonably easily calculated so lets have a go.
For every 100 miles driven one will save 10 minutes in travel time (75 mins, down from 85 mins). This does of course depend on having a clear road and no holdups due to crashes.
Lets look at the ‘costs’. According to a review of changes to speed limits conducted for the authorities in British Columbian 2003 the rate of crashes and fatalities is likely to increase significantly. They don’t report on any countries increasing speed from 70 mph to 80 mph (110km/h to 130km/h). They do however report on when Switzerland reduced its speed from 130km/h to 120km/h with reduced fatalities by 12% and when Sweden reduced speeds from 110km/h to 90km/h and fatalities declined by 21%. Also interestingly when the UK reduced speeds from 100km/h to 80km/h and saw a reduction of 14%.
By contrast when Australia increased its speed limit from 100 km/h to 110 km/h it saw an increase in fatalities of 25%. Increasing speeds in the USA from 89km/h to 105 km/h often had associated increases in fatalities of about 20%.
The Wikipedia Road Safety Article has a useful table which shows motorway casualty rates in the first column and speed limits in the right column (this is not properly referenced though). Is it just me or is it significant that all the worst countries have high speed limits and all the most safe countries have low ones?
Do also check the excellent UK Speed Limit article which has a lot of detail of the history of UK speed limits and which is fully referenced.
So, lets get back to an estimate of the ‘costs’. In 2008 there were 158 fatalities on Motorways. As a rough indicator based on the above research, it looks like we can expect about 30 more fatalities. There are many other costs not yet considered including: increased fuel usage, more road noise, more carbon emissions, more stress, more delays caused by crashes. These concerns are echoed by the AA Trust who warned back in 2005 against a blanket increase in the motorway speed limit to 80mph saying that in the absence of strict enforcement to would lead to “unacceptable enforcement drift to 90 mph” – which would “increase the risk of accidents and raise the total of fatal and serious injuries”.
Incidentally, almost half of UK drivers wanted vehicles to be fitted with Speed Limiters which are already used on trunks which are limited to 56 mph and on express coaches at 65 mph which will also be using the motorways.
There there is the research study conducted by the Institute of Advanced Motorists and the RAC Foundation back in 2006 found that some 26% of motorway drivers were following the vehicle in front too closely and that on the M4 the figure was 50%. Do we really want people tailgating at 90 mph?
The ‘cost’ is some 30 deaths and more crashes, which, errr.. might actually reduce the benefit by creating more hold-ups. Also, increased road noise, fuel consumption and driver stress. The benefit is some 10 minutes off journey times per 100 miles (assuming that there are no congestion, road works or crashes to contend with).
At this point transport consultants would convert these costs and benefits into money using standard calculations used by transport planners. I won’t do this because I don’t have the figures to hand and I find the idea rather offensive.
Finally, here is a chart showing road deaths on UK roads since 1929. Be aware that it was a nasty Labour government that introduced the 70mph speed limit in the 1960s after some terrible crashes in fog. since then fatalities have reduced impressively over the past 40 years under both Labour and Conservative governments. Is this trend going to continue going down or are all these ‘motoring’ biased initiatives (such as removing school crossing patrols, re-timing lights in favour of motorists, increasing speed limits, cutting back on bus services, bus lanes and cycle lanes), are we going to see the graph turn up again. I do do hope that this in not going to be the case.
What I would like to is see now is someone doing a FOI request on the Department for Transport requesting their official report on the subject. There is the nice WhatDoTheyKnow website that makes this very easy to do.