The Three Truck Platooning Task (3TPT) is a variant of the Three Vehicle Platoon Task for truck driving. It contains also additional performance measures and experimental design features.
The driving task resembled driving a truck on a straight rural two-lane motorway. The participants’ vehicle is located in the middle of a truck platoon that consists of three trucks in total, i.e. there is one truck ahead and one truck at the back of the participants’ truck (which is always visible in the side mirrors). The weather conditions are by default configured to sunny and dry and there is no other traffic besides the truck platoon. As the road is perfectly straight, crosswind occurs from time to time to increase steering difficulty. The maximum speed of the participants’ truck is set to 90 km/h. Figure 1 shows the initial driving situation.
Figure 1. Initial 3TPT driving situation.
The participants are allowed to adjust their speed freely, but should be instructed to drive at the speed limit of 80 km/h at all times, if possible. Also, they always have to stay in the middle of the right lane and keep 50 meters to the leading truck whenever possible. The computer-controlled vehicles are programmed to adapt to the speed of the participants’ vehicle, but only within the speed limit (80 km/h).
In addition to this initial driving situation, there are four repeated and randomly distributed events that the participants have to react upon. Firstly, a strong brake event, where the leading truck activated its brake lights and decelerated quickly to 40 km/h. The required reaction is to brake as fast as possible and keep the safety distance (50 meters). Subsequently, the leading vehicle accelerates again and the initial situation (speed 80 km/h, distance 50 meters) has to be re-established. Secondly, a slight break event, where the leading truck decelerats to 50 km/h without activating its break lights. The required reaction is to perform the same reaction as in the break event. Thirdly, a signal detection event, where the leading truck activats its hazard lights for 4.5 seconds. Hereupon, the required reaction is to push a button on the steering wheel. Fourthly and finally, there is another signal detection event, where the following truck activats its hazard lights for 4.5 seconds. The required reaction is also to push the button on the steering wheel.
Data analysis is based on the following raw data: (1) lateral position (relative to the centre of the right lane), (2) longitudinal position (relative to the leading vehicle), (3) steering movements, (4) vehicle speed, and (5) reaction performance. From the variables mentioned above, the following respective variables are computed for analysis:
· Lateral position:
o Standard deviation of lateral position (SDLP)
o Time to line crossing (TLC), i.e. the time to cross either lane with any of the wheels of the vehicle, given constant speed and steer angle. As perfectly straight driving results in TLC values that tend to infinite, values above 20 seconds were excluded from analysis.
o Lane exceedances (LANEX)
· Longitudinal position:
o Distance Headway (DHW), i.e. the distance to the leading vehicle.
o Time Headway (THW), i.e. the hypothetical time to arrive at the position of the leading vehicle if it would stop immediately. For analysis, values above 10 seconds were excluded.
o Time to collision (TTC), i.e. the time until the vehicle would crash into the leading vehicle if both speeds were kept constant. Only values less than five seconds were considered.
· Steering movements:
o Steering wheel reversal rate (SRR)
o Standard deviation of steering wheel angle
o Zero crossings of steering wheel angle
· Vehicle speed:
o Average speed
o Standard deviation of speed
o Maximum speed
· Reaction performance:
o Reaction time
In addition, you can manipulate stress within the driving task by means of an unexpected event, which occurred only once by the end of the second test trial. Hereto, the leading truck unforeseeably dropps a cargo load of boxes directly on the driving lane in front of the participants’ truck.