The government of France insisted 400 lives would be saved annually after it lowered the speed limit on departmental roads to 80km/h (50 MPH) in July. The pro-motorist group 40 Million Motorists in November looked at the issue from another angle and asked, how much does that policy of lowering speed limits cost the public in terms of lost productivity?

The group formed a committee of independent academics, lawyers and representatives from the motoring community to examine the question, reviewing as much data as were available -- the effort was hindered by French officials who denied requests for access to more complete accident data. The committee released the first draft of a report and invited comments and revisions from the public.

On a simple mechanical level, attempting to force traffic to drive 6 MPH slower on heavily trafficked roadways causes the public to spend more time on the road. From studies, the actual reduction in speed from a 10km/h drop in the posted limit is, on average, 4.4km/h or 2.6 MPH. Using traffic counts on the roads in question, the group calculated motorists will spend an extra 300 million hours on the road, which is equal to the productive output of 200,000 workers every year, valued at 4.4 billion euros (US $5 billion).

Even accepting without question the government's claim about the number of lives saved, the economic value of the improvement in safety is 600 million euros (US $687 million), leaving a net cost to the lowered speed limit policy of 3.8 billion euros (US $4.4 billion) annually.

The report points out that the government has a legal duty to perform a true cost-benefit analysis before implementing a major public policy initiative like the department-wide lowering of the speed limit, which affects 235,000 miles of road. The evaluation of the speed limit change, conducted under the guidance of economist Remy Prud'homme, followed the recommended procedures for evaluating policy costs.

"The 80km/h speed reduction will unfortunately not achieve the government's goal of a decline in road traffic deaths of 400," said Jean-Luc Michaud, the chairman of the committee that produced the report. "Moreover, the study shows that this foreseeable failure will be aggravated by 200,000 years lost on the roads, which represents a final net cost of 3.8 billion euros per year, which will penalize the economy and the residents of the country's most fragile regions."

A copy of the report is available in a 1mb PDF file at the source link below.