Thursday, February 19, 2009

Perceptual Countermeasures Simulator Approach

On-road testing of new treatments can be problematic if they have not been shown to be a benefit first in an off-road test environment. A driving simulator is an ideal test environment as it provides a safe, inexpensive and ethical facility to address these issues.

The driving simulator at MUARC was developed by the Transport Accident Commission using the latest silicon graphics projections and provides a 180 degree front view as well as a rear image. The simulator also provides "road feel" through three positive feedback dampers under the car and a quadraphonic sound system. From earlier work, the simulator had been shown to be a valid test environment for evaluating PCMs.

A number of participants were recruited to "drive" the simulator and a total of seven human factor experiments were conducted to test systematically a range of PCMs, including:

* Transverse road markings;
* Lane edge & herringbone treatments;
* The Drenthe province treatment from the Netherlands;
* Centreline and other edgeline treatments; and
* Several enhanced curvature treatments.

Drivers drove a series of test tracks which had previously been programmed to include similar treated and untreated road locations. Speed and lateral position measures were compared at both the treated and untreated locations. Differences were tested statistically to demonstrate significance using Analysis of Variance techniques.
Transverse lines

Transverse lines are high contrast, painted or thermo-plastic strips about 60cm wide that are placed across the driving lane for up to 400m on the approach to an intersection or hazard. They are generally spaced at decreasing spacings in the direction of travel.

The results from this study showed that transverse lines can be effective at reducing travel speed by up to 11 km/h, both immediately after entering the treatment zone (suggesting an alerting effect) as well as throughout the treatment area (consistent with a perceptual effect). However, it did not seem to matter if the transverse lines were at decreasing or constant spacings.

A half Wundt Illusion treatment (forward facing chevrons across the lane) had little effect on travel speed compared to transverse lines.

Lane Edge & Herringbone Treatment

Peripheral transverse lines (approximately 60cm from the lane edge) also resulted in significant speed reductions on the approach to an intersection, although not as large as the full-width lane lines.

A herringbone pavement marking system with decreasing line frequency had been previously suggested as a PCM to speeding in the lead-up to a road hazard. This was a variation of peripheral transverse lines angled at approximately 45deg to the edgeline that can be placed either pointing towards the approaching vehicle or away from it.

The results showed some speed reductions for herringbone edgeline treatments, similar to those for the peripheral transverse lines above. In addition, it did not seem to matter if these lines were perpendicular to the edge of the road or slanted either towards or away from the driver.

A novel tree planting alongside the road at diminishing spacings had no effect on travel speed.

The Drenthe Province Treatment

This treatment was first developed in the Netherlands and has been used there to counter speeding on 80 km/h rural highways.

The standard version comprises a gravel centreline (with while intermittent strips) as well as intermittent gravel edgeline treatments and provides 2.25m of free road surface between these treatments. Variations of the Drenthe treatment examined here included white painted edgeline treatments (no gravel) and solid gravel edgeline treatment.

The results showed that only the standard Drenthe treatment elicited significant speed reductions of up to 2 km/h but did cause vehicles to move 16 cm closer to oncoming traffic. Other variations failed to produce significant speed reductions.

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