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

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• 1.

### According to Gerberich, et al. (1996), 65% of all farm tractor crashes were rear-end collisions in low light and only 24% of crashes in daylight were rear enders.  What is NOT likely the cause for this disparity?

• A.

Farm tractors do not typically present a good pattern at night

• B.

Farm tractors typically travel much slower than other traffic

• C.

Explanation
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.

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• 2.

### According to Sun & Benekohal, the average driver follows how close to the lead vehicle?

• A.

1.0 second or less

• B.

1.25 to 1.5 seconds behind

• C.

2.0 seconds behind or more

B. 1.25 to 1.5 seconds behind
Explanation
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.

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• 3.

### Based upon the research by McGehee et al. (1997); Knipling et al. (1993); Sorock et al. (1996) and Dingus et al. (2007), we learned that the vast majority of rear-end collisions involve a lead vehicle that is stopped.

• A.

True

• B.

False

A. True
Explanation
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.

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• 4.

### When evaluating the relationship between hazard detection (of a stopped or slow LV) versus the distance necessary to avoid, we can see that drivers face a dangerous (high-speed crash) situation when...

• A.

• B.

The relative velocity (closing speed) is greater than 30 mph

• C.

The approaching driver is following the lead vehicle and the lead vehicle stops

• D.

A lead vehicle is stopped at the apex (peak) of a curve

B. The relative velocity (closing speed) is greater than 30 mph
Explanation
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.

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• 5.

### If the lead vehicle we have been following brakes suddenly, the average response time has been near 1 second.  This is because we have the opportunity to see...

• A.

• B.

Immediate change in closing speed

• C.

Brake lights going on

• D.

All of the above

D. All of the above
Explanation
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.

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• 6.

### Based upon the research by Fisher & Hall; Schriener et al.; Crawford; Boff & Lincoln...

• A.

Flashing, presence and strobe lights had no influence on REACTION time

• B.

Reaction time decreases by 10% due to flashing lights

• C.

Flashing lights improve performance when eccentricity equals zero

A. Flashing, presence and strobe lights had no influence on REACTION time
Explanation
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.

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• 7.

### Summala, Lamble & Laasko's results suggest (after considering eccentricity) that brake lights were associated with a...

• A.

Faster response time of 0.3 seconds

• B.

Slower response time of 0.3 seconds

• C.

Faster response time of 0.1 seconds

A. Faster response time of 0.3 seconds
Explanation
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.

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• 8.

### Subtended angular velocity or visual expansion rate of 0.003 compared to 0.006 means the following:

• A.

• B.

0.003 involves real-life drivers and 0.006 does not

• C.

0.003 refers to radians per second and 0.006 refers to degrees per second

A. 0.003 radians per second is farther away from the lead vehicle than 0.006 radians per second
Explanation
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.

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• 9.

### When subtended angular velocity (visual expansion rate) was less than 0.0035r/s (further away), the average REPORTED response time from several studies was...

• A.

0.98 sec

• B.

2.11 sec

• C.

3.52 sec

C. 3.52 sec
Explanation
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.

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• 10.

### Once a driver closed to a position within 0.007 radians per second, the average response time (based upon several studies in Part 1 of SAE 2005-01-0427) was...

• A.

1.16 sec

• B.

2.11 sec

• C.

4.11 sec

A. 1.16 sec
Explanation
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.

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• 11.

### When a driver realizes he is closing on a lead vehicle on a multi-lane highway, one of his first responses is usually to...

• A.

Slow down

• B.

Speed up

• C.

Anticipate passing and maybe look toward a mirror

C. Anticipate passing and maybe look toward a mirror
Explanation
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.

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• 12.

### The Liebowitz hypothesis says that...

• A.

Lead vehicles are relatively intense stimuli

• B.

Large objects seem to move slower

• C.

Large objects seem to move faster

B. Large objects seem to move slower
Explanation
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.

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• 13.

### According to Sullivan et al. (2003), trucks are 8 times more likely to be involved in a rear-end collision at night.

• A.

True

• B.

False

A. True
Explanation
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.

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• 14.

### 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...

• A.

3 sec

• B.

5 sec

• C.

7 sec

C. 7 sec
Explanation
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.

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• 15.

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

• A.

40 %

• B.

75 %

• C.

90 %

A. 40 %
Explanation
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.

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• 16.

### Topography has been shown to be an expectancy term.  This means that when there is a LV stopped on a straight segment of road, it is more expected and easier to discern than if that vehicle were stopped at an intersection.  Essentially, response times are greater at intersections.

• A.

True

• B.

False

B. False
Explanation
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.

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• 17.

### If we compare the rear-end crash rate headed up to a bridge with the same mile markers for traffic in the opposite direction, we usually find that there are far more rear-end crashes in the direction heading up to the bridge.

• A.

True

• B.

False

A. True
Explanation
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.

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• 18.

### Which is NOT true of headway?

• A.

• B.

Headway is the distance in seconds that an approaching vehicle is behind a LV

• C.

PRT increases by 0.39 seconds for every 1 second headway on straight roads

• D.

When there is changing topography, intersections, or other cues to determine the closing speed with the LV, headway has the most influence

D. When there is changing topography, intersections, or other cues to determine the closing speed with the LV, headway has the most influence
• 19.

### What is the VER threshold (distance behind the Lead Vehicle)? Discernable width of the LV = 6 ft (1.8 m) Lead vehicle speed = 10 mph (16 km/h) Approaching vehicle traveling 50 mph (80 km/h) VER threshold = 0.006 radians / sec   VER Dist = SQRT[(w x Relative velocity)/VER angle]

• A.

200 ft (61 m) (+/-6 ft., 2 m)

• B.

242 ft (74 m) (+/-6 ft., 2 m)

• C.

303 ft (92 m) (+/-6 ft., 2 m)

B. 242 ft (74 m) (+/-6 ft., 2 m)
Explanation
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.

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• 20.

### Using the previous question, if PRT = 2.0 sec and the driver’s eyes are 8 ft. (2.4 m) from the front bumper, what is the pre-impact maneuver we would expect to see (if this driver responded as did the average driver)? Expected Response = VER threshold x Appr V / Relative V - Dist eyes to bumper - PRT x V

• A.

102 ft (31 m) (+/-6 ft., 2 m)

• B.

148 ft (45 m) (+/-6 ft., 2 m)

• C.

216 ft (66 m)(+/-6 ft., 2 m)

B. 148 ft (45 m) (+/-6 ft., 2 m)
Explanation
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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• 21.

### The driver (responder) is stopped at a stop sign and sees a train approaching.  Which would probably be the best subtended angular velocity threshold (based upon forced choice studies) for this situation?

• A.

0.002 to 0.003 r/s

• B.

0.004 to 0.006 r/s

• C.

0.006 to 0.009 r/s

A. 0.002 to 0.003 r/s
• 22.

### The 100-Car Study (Dingus and Klauer) showed that every one of the rear-end crashes involved a LV that was stopped and no driver struck a LV that was decelerating.

• A.

True

• B.

False

A. True
Explanation
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.

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• 23.

### If there is inadequate context to determine that the LV is stopped (if on a flat and straight road), you should use the VER threshold to determine when the hazard was perceivable.

• A.

True

• B.

False

A. True
Explanation
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.

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• Current Version
• Mar 18, 2023
Quiz Edited by
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• Jan 06, 2012
Quiz Created by
CSRG

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