While this statement is true, the frequency with which it is used in road safety enforcement and education is out of all proportion to its actual role in the road toll. Part of the problem is that a speed related crash is actually defined as "travelling too fast for the conditions". This definition was chosen by the Ministry of Transport in 1930 because it summarises the extant legal definition of a speeding offence, which was introduced in the Motor Traffic Regulations in 1906. The fact that speeding was originally referred to as the offence of "furious driving" in the road rules of 1876 suggests that it is also an easy factor to identify in accidents and may be over represented relative to other driver errors for this reason. It also notable that when law enforcement officers investigate car crashes they identify unlawful acts much more often than other driver errors or road faults.

The road tolls in recent years have been similar to the road tolls in the early 1960s despite three times as much traffic and a 32% increase in open road average speeds. This increase in average speeds has been enough to triple the road toll, which is exactly in line with the claim that a 1% increase in average speeds results in an increase in road deaths of between 3% and 5% (ie an increase in average speeds from 100km/h to 120km/h will double the the number of road deaths). The combined effect of more traffic and higher average speeds is that the road toll in 2004 was actually nine times worse than the road toll would have been in 1964 if todays cars, roads, vehicle occupancy rate and attitudes to seatbelts had been available in 1964. There are two ways of looking at this effect on the number of deaths. Without these last mentioned improvements almost 4,500 people would have died on our roads last year rather than 480, a saving of over 4,000 lives. Without the increase in both traffic and average speeds only 50 people would have died on our roads last year rather then 480, a saving of 430 lives. Therefore roughly 200 lives would have been saved if average speeds had not increased since 1964 whereas 4000 lives were saved because the crashworthiness of the average car has increased since 1964.

On the basis that a picture is worth a thousand words several graphs are presented below.

Regional speed related deaths - Shattering illusions: saving lives, LTSA, 1997
Regional speed survey results - Motor Accidents in New Zealand, LTSA, 1998
National speed survey results 1960-1976 - The 50 mph Speed Limit, MoT, 1979, Journal of Accident and Injury Prevention.
National speed survey results 1982-2004 - LTSA spreadsheet.
Speeding infringements - New Zealand Yearbooks 1960-2004
Capital Investment - Annual reports, National Roads Board/Transit/Transfund, 1985-1995
State Highway kilometres - Roading Statistics, Transfund, 1995
Vehicle km travelled 1960-1987 - Motor Accidents in New Zealand, LTSA, 1987
Rural vehicle km travelled 1960-1990 - New Zealand Yearbook 1994
Vehicle km travelled 1990-2004 - National Traffic Database, Ministry of Transport, 1996-2005