National Free Speed Surveys

Monitoring Road Safety In New Zealand

Most New Zealanders will be familiar with the Government’s ongoing campaign to highlight the dangers of speeding.

The annual cost of speed related crashes is estimated at around $675 million (Ministry of Transport, 2011), although the social cost can be much higher. We have a mix of urban and rural roads, and a wide range of driving environments, surfaces, and maintenance requirements. Understanding driver behaviour around speeding involves pulling together a complex set of variables to provide a useful set of data, with the ultimate aim of saving lives.

In 1996, the Ministry of Transport (MoT) began undertaking an annual Free Speed Survey to monitor safety and driver behaviour on New Zealand roads. WSP Opus Research has been responsible for carrying out the survey since it started, with the last survey completed in September 2012 and the next starting in July 2013. Free speeds are those where only vehicles not impeded by others are measured, and at sites not limited by the road geometry. They are particularly important as they indicate a driver’s preference or desire around speed. Surveys are undertaken during off-peak periods and during the school term to reflect normal weekday patterns.

The survey involves WSP Opus staff taking measurements at 137 sites across the country using laser speed guns or digitectors with tribo-electric cables, as well as counting traffic flow and vehicle types. The survey sites include 71 rural and 66 urban areas with both 100km/h and 50km/h speed limits. WSP Opus staff from Auckland, Paeroa, Gisborne, Wanganui, Blenheim, Invercargill and Wellington collect data, which is then collated by WSP Opus Research staff and reported to the MoT. Changes in recorded speeds over time allow the MoT to measure the success of speed management interventions. The Ministry can then direct resources appropriately to enforcement, education and design.

Since the survey started 17 years ago, the percentage of cars driving over the speed limit in 100km/h areas has decreased from 56% to 25%. On 50km/h roads, this has decreased from 82% to 53%, emphasising the success of measures that have been implemented over that time to decrease open road speeds and draw attention to urban speed compliance.

Success for this project relies not only on technical expertise and logistics, but also great communication and coordination between seven WSP Opus offices around New Zealand.

The Free Speed Survey is an important tool in monitoring and influencing road safety in New Zealand, and WSP Opus is proud of its contribution to helping save lives.