The effects of improved vehicle technology on the design of acceleration and deceleration lanes at freeway entry and exit ramps

The effects of improved vehicle technology on the design of acceleration and deceleration lanes at freeway entry and exit ramps

An important aspect of road geometry design is the provision of safe distances to allow motorists to change speed from low or moderate speed flows to high speed flows, and vice versa. Design guidelines for determining acceleration and deceleration lane lengths were evaluated to
understand the basis for these designs from across the world. It was found that many current guidelines are based on data collected over 40 years ago. Vehicle acceleration and deceleration characteristics have changed over this period and the majority of the Australian vehicle fleet is
less than 10 years old. Data was collected from a number of sites in the Newcastle and Central Coast regions of New
South Wales using a combination of video and GPS to measure the performance of passenger vehicles and an associated driver characteristic. The GPS recorded real position at regular time intervals which was used to calculate acceleration or deceleration rates of passenger vehicles.
The results were used to determine a driver characteristic which indicated how much of the acceleration and deceleration vehicle performance the average driver was willing to use.
An acceleration model and a deceleration model were developed based on vehicle dynamics. The models output distance and time required to reach target speeds. The parameters for each model to reproduce the guidelines used in the Austroads Guide to Road Design were derived.
Preliminary results indicated that most drivers tend to use all of the acceleration or deceleration lane length currently provided, rather than to utilise the increased vehicle performance available to them. An important feature of the models is that they allow for the use of actual vertical geometry instead of average grades used in former models.

© ARRB Group Ltd and Authors 2012. The Author allows the conference host, ARRB Group Ltd, to publish the works submitted for the 25th ARRB Conference, hereby granting ARRB the non-exclusive right to publish the work in printed, electronic or online formats.