Ch. 5 Section 5.6, 5.7, & 5.8 Response To Lead Vehicles

The given statement is true. According to the research conducted by McGehee et al. (1997), Knipling et al. (1993), Sorock et al. (1996), and Dingus et al. (2007), it has been found that most rear-end collisions involve a lead vehicle that is stopped. This suggests that the majority of rear-end collisions occur when a vehicle in front comes to a halt, and the following vehicle fails to stop in time, resulting in a collision.

The explanation for the given correct answer is that Sullivan et al. (2003) found that trucks are 8 times more likely to be involved in a rear-end collision at night. This suggests that there is a higher risk of rear-end collisions involving trucks during nighttime compared to other times of the day.

The research conducted by Fisher & Hall, Schriener et al., Crawford, and Boff & Lincoln found that the presence of flashing, presence, and strobe lights did not have any impact on reaction time. This means that the reaction time of individuals was not affected by the presence or absence of these types of lights.

The given answer correctly explains that a subtended angular velocity or visual expansion rate of 0.003 radians per second is farther away from the lead vehicle compared to 0.006 radians per second. This means that the object with a lower angular velocity is at a greater distance from the observer.

Based on several studies in Part 1 of SAE 2005-01-0427, it was found that once a driver closed to a position within 0.007 radians per second, the average response time was 1.16 seconds.

According to Lee, Olson & Wierwille (2002), the average driver spends 40% of his time looking ahead in the three seconds before moving laterally in response to a slow moving lead vehicle.

The explanation for the given correct answer is that there are usually more rear-end crashes in the direction heading up to the bridge because drivers tend to slow down or brake when approaching a bridge. This sudden change in speed can catch other drivers off guard, leading to rear-end collisions. Additionally, drivers may also be distracted by the bridge itself, causing them to not pay enough attention to the traffic in front of them.

The explanation for the answer "False" is that the statement in the question is incorrect. The question states that topography has been shown to be an expectancy term, implying that it affects response times at intersections. However, the correct statement is that response times are actually greater at intersections, not on straight segments of road. Therefore, the answer is false.

The VER threshold is calculated using the formula VER Dist = SQRT[(w x Relative velocity)/VER angle]. In this case, the discernable width of the Lead Vehicle is given as 6 ft (1.8 m), the Lead Vehicle speed is 10 mph (16 km/h), and the approaching vehicle is traveling at 50 mph (80 km/h). The VER threshold is given as 0.006 radians / sec. Plugging these values into the formula, we can calculate the VER Dist. The answer option 242 ft (74 m) (+/-6 ft., 2 m) is the correct answer as it falls within the range of possible distances behind the Lead Vehicle.

The 100-Car Study conducted by Dingus and Klauer found that all the rear-end crashes involved a leading vehicle (LV) that was completely stopped, and no driver struck a LV that was decelerating. This means that in all the rear-end crashes analyzed in the study, the LVs involved were stationary and not in the process of slowing down. Therefore, the statement is true.

This statement is true because if there is not enough context to determine whether the Lead Vehicle (LV) is stopped or not, the VER threshold can be used to determine when the hazard was perceivable. The VER threshold refers to the point at which a hazard becomes noticeable or perceptible to the driver. By using this threshold, one can determine when the hazard of the LV being stopped becomes perceivable, even in situations where there is inadequate context to make a clear determination.

When the lead vehicle brakes suddenly, we have the opportunity to observe multiple cues that indicate the need for us to respond. We can perceive the pitch of the lead vehicle, which may change as it decelerates. We can also notice an immediate change in the closing speed between our vehicle and the lead vehicle. Additionally, we can see the brake lights of the lead vehicle turning on, which is a clear indication of braking. Therefore, all of these cues contribute to our average response time of around 1 second in such situations.

The Liebowitz hypothesis suggests that large objects appear to move slower. This means that when comparing the speed of different objects, larger objects are perceived as moving at a slower pace than smaller objects. This hypothesis implies that our perception of motion is influenced by the size of the object in question.

According to Sun & Benekohal, the average driver typically follows the lead vehicle at a distance of 1.25 to 1.5 seconds behind. This means that there is a reasonable gap maintained between the two vehicles, allowing for a safe following distance. This distance is important to ensure that the driver has enough time to react and stop in case of any sudden changes or emergencies on the road.

When the relative velocity (closing speed) between the approaching driver and the lead vehicle is greater than 30 mph, it indicates that the speed at which the approaching driver is moving towards the lead vehicle is significantly high. This suggests that the approaching driver may not have enough time to react and apply the brakes to avoid a collision if the lead vehicle suddenly stops. Therefore, when the relative velocity exceeds 30 mph, the situation becomes dangerous and increases the risk of a high-speed crash.

Summala, Lamble, and Laasko's results indicate that brake lights were linked to a faster response time of 0.3 seconds. This means that when drivers saw brake lights, they reacted more quickly compared to when brake lights were not present. The study suggests that the presence of brake lights can significantly improve drivers' reaction time, potentially preventing accidents or reducing the severity of collisions.

The correct answer is 3.52 sec. This suggests that when the visual expansion rate is less than 0.0035r/s (further away), the average reported response time from several studies is 3.52 seconds.

When a driver realizes he is closing on a lead vehicle on a multi-lane highway, one of his first responses is usually to anticipate passing and maybe look toward a mirror. This is because the driver needs to assess the situation and determine if it is safe to pass the lead vehicle. By anticipating the passing maneuver, the driver can start planning and preparing for the lane change. Looking toward a mirror allows the driver to check for any vehicles approaching from behind, ensuring that it is safe to change lanes.

Based on the given equation, the expected response for the pre-impact maneuver depends on various factors such as the VER threshold, the approach velocity (Appr V), the relative velocity (Relative V), the distance from the driver's eyes to the front bumper, and the perception-reaction time (PRT) multiplied by the velocity (V). By substituting the given values into the equation, the expected response is calculated to be 148 ft (45 m) with a margin of error of +/- 6 ft (2 m).

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The given answer, "Drivers follow too close," is not likely the cause for the disparity in rear-end collisions between low light and daylight conditions. This is because the question states that 65% of farm tractor crashes in low light were rear-end collisions, while only 24% of crashes in daylight were rear-enders. This suggests that there is a higher likelihood of rear-end collisions in low light conditions regardless of driver behavior. Therefore, the cause for the disparity is not likely to be related to drivers following too closely.

According to Henning et al. (2007), the 50th percentile thinking time prior to the start of a lane change (in response to a slower moving lead vehicle) is 7 seconds.