Participación social juvenil

2.2.2.1 Driving Simulator

Both hazard perception tests took place in UCC’s driving simulator, which consists of a full-size Volkswagen Polo vehicle with manual transmission. It has 7.1 Dolby surround sound and a 135 degree field of view, resulting from image projection onto three wall-to-floor screens located approximately one to one-and-a-half metres from the car body. This immersive, fully interactive, visual environment is supplemented with active wing and rear view mirrors. A network of five PCs underlie the STISIM 400W and permit the real time display of complex traffic scenes, including other traffic, and pedestrians who behave realistically in response to the simulator-drivers’ actions. Simulator output includes information on driver’s speed, road position, and all pedal, steering wheel and ancillary dashboard controls at 20Hz.

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Figure 3: STISIM 400W Driving Simulator

2.2.2.2 Tests of Hazard Detection and Hazard Handling

The same hazard perception drive was used in both the detection and handling conditions. The drive consisted of five different speed zones i.e. 25kph, 40kph, 60kph, 70kph and 100kph; each containing various types of hazards including bends of different curvature, traffic lights with amber onset at different times, visible and hidden pedestrians, car emerging events and following tasks. The speed zones were counterbalanced to control for any ordering effects as follows:

Drive 1: 40kph, 100kph, 25kph, 70kph, 60kph Drive 2: 60kph, 25kph, 70kph, 40kph, 100kph Drive 3: 25kph, 60kph, 40kph, 100kph, 70kph Drive 4: 70kph, 25kph, 60kph, 100kph, 40kph

The hazards included in the drive were selected based on an analysis of the Road Safety Authority (RSA) accident database which consists of information on all recorded accidents on Irish roads from 1997-2007, along with information from the literature on previously effective hazards. Based on these analyses five types of hazard were included in the hazard perception tests. These were car emerging events, merging traffic events, pedestrian events, traffic light events, and bends. The drives took place on a two-lane road (lane width=3.66m), which moved through both rural and urban environments.

2.2.2.2.1 Car Emerging Events

For car emerging events, a car parked perpendicular to the road emerged in front of the participant as they approach.

Figure 4: Example of Car Emerging Event

The car was initially parked 8.6 metres from the roadway dividing line, and started to move when the participant was 4 seconds away. The car moved 4.3 metres into the roadway, partially blocking the driver’s lane (see Figure 4). There were a total of three car emerging events in the drive (25kph, 40kph, 100kph).

2.2.2.2.2 Merging Traffic Events

In the merging traffic events, a car parked parallel to the road suddenly pulled out from the near side of the road to enter the traffic flow, travelling at the posted speed limit. The car began to move when the participant was 3 seconds away (see Figure 5).

17/12/2013 Ruth Madigan 42 There were four merging traffic events in the drive, one in the 25kph, 40kph, 70kph and 100kph speed-zones.

2.2.2.2.3 Pedestrian Events

In the pedestrian events a pedestrian walked out in front of the driver from the near side of the road and crossed to the opposite side of the road. There were two categories of pedestrian. Pedestrians with continuous visibility pedestrians were fully visible for the entire walking time before the driver reached them. The pedestrian was initially located 6.1m from the centre-line of the road, and started to move at a speed of 1.07m/s when the participant was 3 seconds away (see Figure 6). Pedestrians with interrupted visibility emerged from behind a parked van/truck. The pedestrian was initially located 12.2 metres from the centre of the road and started to move at a speed of 1.52m/s when the participant was 8 seconds away. They disappeared behind the parked vehicle for 1 second of their trajectory time.

Figure 6: Example of Pedestrian event with continuous visibility

There were a total of six pedestrian events, with one pedestrian with continuous visibility in each of the 25kph, 40kph and 70kph speed zones; and one pedestrian with interrupted visibility in the 40kph, 60kph, and 100kph speed zones.

2.2.2.2.4 Traffic Lights

Amber onset occurred when the driver was in different decision zones with respect to the traffic lights (safe stopping, dilemma, & safe crossing zones, see Figure 7). The

timing of amber onset in each of the speed zones was calculated using the following formulae from Papaioannou (2007):

Safe stopping zone (SSZ) = Vop + (v₀²/2dm) Safe crossing zone (SCZ) = VoՇ – (w + l)

Dilemma zone = SSZ - SCZ

Where Vo is the approaching speed of the vehicle, p the perception/reaction time, dm the maximum deceleration, Շ the yellow time interval, w the width of the crossing road, and l is the vehicle length. A deceleration rate of 3.5 m/s² was used as representative of the majority of vehicles, and the perception/reaction time was taken as equal to 1.5s based on Papaioannou’s (2007) research. The width of the crossing was 9.86m and the length of the vehicle was 4.17m. Table 2 shows the amber onset time for all three types of traffic lights across the various speed zones.

Table 2: Amber onset times for traffic lights in different speed-zones

Traffic Light Zone 25kph 40kph 60kph 70kph 100kph

Safe Stopping Zone 2.49s 3.09s 3.88s 4.17s 5.47s

Dilemma Zone 1.73s 2.35s 3.01s 3.25s 3.97s

Safe Crossing Zone 0.98s 1.74s 2.16s 2.28s 2.49s

Amber onset for traffic lights classified as being in the safe stopping zone occurred when participants’ were far enough away from the traffic light that most people would be expected to come to a stop. For traffic lights classified as being in the safe crossing zone, amber onset occurred when participants were so close to the traffic light that most people could go straight through the intersection without any acceleration. Finally, amber onset classified as the dilemma zone occurred where neither decision was obvious as drivers would have to brake abruptly to come to a stop, or increase speed rapidly to clear the intersection

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Figure 7: Example of Traffic Light Event

There were a total of 12 traffic light events, three in each speed zone.

2.2.2.2.5 Bends

Participants drive through a series of bends, some of which had interrupted visibility (see Figure 9) and some of which had continuous visibility (see Figure 8).

Table 3: Radius of curvature for bends in different speed zones

Curvature 25kph 40kph 60kph 70kph 100kph

Small 20m 30m 70m 100m 340m

Medium 35m 50m 170m 200m 660m

Large 50m 65m 190m 320m 880m

Bends with continuous visibility contained no impediments to vision throughout the bend. Bends with interrupted visibility were situated in an urban environment and it was not possible to see the other side of the bend. There were three levels of curvature, small, medium, & large. The radius of the bend depended on the speed zone (see Table 3).

Figure 8: Example of bend with continuous visibility

Figure 9: Example of bend with interrupted visibility

As can be seen in Table 3 bends with small curvature had the smallest radius and therefore, were the most difficult to negotiate. Large bends had a large radius, making them less sharp, and easier to negotiate. There were a total of 30 bend events, six in each speed zone.