Gap acceptance and risk-taking by young and mature drivers, both sober and alcohol-intoxicated, in a simulated driving task Professor: Liu Student: Ruby

Motive Speeding and alcohol still remain the two most factors to fatal road accidents. In 1998, young drivers (17-20) comprised 5.4% license population in New South Wales but almost 15.5% of all fatal overtaking crashes for that year.

Purpose Survey the effects of alcohol on a driver’s perception of speed, hazards and risk acceptance.

References 1.1 Hazard detection a.The novice drivers detected hazards lees quickly and less efficiently. (Deery and Love, 1996) b. The novice drivers look at the road and lane markings close to the hood of their vehicle, but the experienced drivers looked to the horizon and monitored their side position via their peripheral vision. (Mourant and Rockwell, 1970)

References 1.1 Hazard detection c. Young drivers have faster reaction times than mature drivers in non-driving settings. (Summala, 1987) d. Alcohol-affected drivers, especially in young drivers, would be expected to detect approaching vehicles most slowly and this is more prominent in novice drivers. (Deery and love, 1996a, b; Deery, 1999)

References 1.2 Time estimations a.Time to collision show an underestimate of time. (Schiff and Dewiler1979) b.Older drivers (65-83) demonstrated a tendency to underestimate time to contact than younger drivers (20- 45). (Cavallo and Laurent, 1988)

References 1.2 Time estimations c. The judgments about time to collision were less accurate for older drivers (40-64) compared with younger drivers (18-29). (DeLucia et al., 2003) d. Young drivers have a higher rate of accidents involving alcohol. (Triggs and Smith, 1996)

Method 2.1 Participants Young volunteers(16): 8 M and 8 F. age:18-21 Mature volunteers(16):10 M and 6 F age:25-35

Method 2.2 Alcohol--- Alcohol condition (target BAC =0.08g/100ml) Placebo condition (target BAC =0.00g/100ml) Beverage: Vodka mixed orange juice. 20min to finish the beverage. Before 24h can’t drink alcohol.

Method 2.3 Driving simulator: a. STISIM Drive (Version ) b. Visual images were projected onto three screens in 135 degrees field of view.

Method 2.4 Experimental tasks a. Driving simulator in 15 min b. After drinking, wait 40 min than task the following tasks.

Method detection time Press the horn button as soon as they detected an approaching vehicle on the horizon. a.The vehicles were showed on opposing lane by appearing 500m away from behind buildings or 800m away in an area in trees. b.The approaching vehicle speeds were randomized between 50 and 90kph. c.The participant’s speed was limited to keep at 90kph. d.A straight, left curve and a right curve road.

Method When the vehicles would have passed each other, press the horn button. a.Approaching vehicles were appeared in view for 9s then to disappear when they were 3s away from the participant’s vehicles. b.The approaching vehicle speeds were randomized between 50 and 90kph. c.The participant’s speed was limited to keep at 90kph.

Method Overtaking maneuver Requiring to overtake a vehicle being followed. a.The vehicle being followed was kept 80kph. b.The successions of approaching vehicles all at the same speed (50kph-9~17s or 90kph-7~15s) c.The participant’s speed was limited to keep at 100kph.

Results 3.1 Blood alcohol concentration a.There was no significant difference between the mean peak BACs of young and mature participants. b.There was a significant between both of the mean peak BACs and the target BAC of 0.08g/100ml(t(df=15) =−6.127, p < 0.05and t(df=15) =−6.536, p < 0.05).

Results 3.2 Detection time a.A significant main effect of roadway curvature was found on response times to an approaching vehicle (F(1,24) = , p < 0.001)

Results b. Age was significant in a driver’s ability as an interaction with straight and curved sections of road (F(1,24) = 8.92, p < 0.01).

Results c. Alcohol also significantly (F(1,31) = 4.94,p < 0.05) interacted with detection times.

Results d. A similar significant interaction(F(1,24) = 42.38, p < 0.001) whereby all participants were slower in detecting the presence of approaching vehicles on curved roadways.

Results 3.3 Time to collision Time to collision was always underestimated. a. A significant effect (F(1,24) = 44.97,p < 0.001) was observed with approaching vehicle speed.

Results b. Male drivers underestimated TTC to a significantly (F(1,28) = 4.36, p < 0.05) lesser extent than female drivers.

Results 3.4 Overtaking task a. A significant age interaction (F(1,20) = 13.15, p < 0.005) with the speed of approaching vehicles.

Results b. Female drivers created significantly (F(1,20) = 6.66, p < 0.05) larger headway distances (16.48m versus m) between their vehicle and the vehicle being overtaken than the male drivers.

Results c. A significant overall effect of age was found with mean speed (F(1,28) = 6.24,p < 0.05).

Discussion 4.1 Detection time a.On straight roads, mature drivers recorded marginally faster vehicle detection, it can be attributed to the variable visual strategies adopted by drivers of different ages and experiences. b.Mature drivers were slower (0.73 s) than young drivers to detect the presence of an approaching vehicle on curved sections of road, perhaps an age-associated increase in reaction time.

Discussion 4.1 Detection time c. The attention demands are greater on curves and the ability to divide attention is decreased after the consumption of alcohol. d. when a vehicle approaches at a fast speed on a curve, there is increased contrast in the driver’s retinal image.

Discussion 4.2 Time to collision a. In considering an approaching vehicle traveling at a faster speed, the rate of change of background environmental and the angular velocity of the approaching vehicle are both increased. This allows the viewer a more accurate perception of the approaching vehicle’s speed, resulting in more accurate (less underestimated) times.

Discussion 4.2 Time to collision b. Females tended to make more conservative estimates of TTC than males. Males, compared with females, have an sensitive sense of their own driving ability and perceive less risk in a variety of dangerous driving behaviors.

Discussion 4.3 Overtaking task a.Mature drivers were less anxious when overtaking in the faster vehicles, perhaps because these vehicles appeared further away. b.Mature participants made overtaking decisions based largely on the relative distance of the approaching vehicle, rather than on relative speed and time.

Discussion 4.3 Overtaking task c.Females spent more time in the opposing lane than males. d. Males have an overconfidence in driving ability all contribute to the relatively riskier behavior.

Discussion 4.3 Overtaking task e. When overtaking in the opposing lane, mature participants adopted faster speeds than young participants, because the experienced drivers showed more caution by making it a priority to return to their own lane as quickly as possible. f. Younger and less experienced drivers tend to overestimate their driving skills and underestimate potential traffic hazards on the road.