We are constantly looking for ways to objectively measure the effect of interventions
One method that has been used successfully by WSP Opus research for almost a decade is the “hands-on” method.
The idea behind the “Hands-On” method is that drivers vary their hand positions based on the level of risk they perceive and the complexity of the environment in which they are driving. When drivers perceive the driving environment is riskier and more complex, they tend to keep their hands on the top half of the steering wheel. When they feel there is less risk – so they are more relaxed – they tend to put their hands on the bottom half of the steering wheel. The method gives us a way to measure how complex the driving task is for the driver, and therefore evaluate what can be done to make the task easier and less prone to driver error.
The “Hands-On” method is simple, shows more variation between drivers than other objective measures such as speed and following distance, and can be adapted to a range of evaluation tasks. From the roadside, and preferably from an inconspicuous and elevated position, two observers independently count the number of hands each driver has on the top half of the steering wheel: two hands, one hand or no hands.
“Hands-On” has been shown to be a sensitive measure of perceived risk. A simple illustration is that drivers keep their hands on the top half of the steering wheel more often when they are driving at 100km/h than when driving at 50km/h, a lower risk situation. Being able to measure drivers’ perceived risk has allowed us to make some useful conclusions. For example, we have found that different driving groups show different behaviours, with drivers of larger vehicles such as SUVs showing a more relaxed hand position than those in smaller vehicles, and men tending to be more relaxed drivers than women.
Potential applications of the results of “Hands-On” surveys are measuring signage interventions, such as variable messages for hazards and incidents, road narrowing and speed interventions, as well as delineation and changes to driver road views. It could also be used to identify roads where drivers tend to take more risks and where more interventions could therefore be considered.
Funded by the NZTA, WSP Opus Research recently evaluated the effectiveness at night time of a series of road marking improvements in the Wellington region. Night vision equipment was needed to compare hand positions before and after the improvements, and the results – that drivers were more relaxed after the environment had been enhanced – demonstrated that the road marking improvements had been a successful undertaking. From NZTA’s point of view, the result shows that investment in bigger, brighter markings can provide an environment that is effectively closer to safer daytime driving in dry conditions.
The full research report for this project can be viewed at: www.nzta.govt.nz/resources/research/reports/442