EXAMPLES
Path Intrusion (Side) Example I

Path Intrusion (Front) [Approaching] Example II

Path Intrusion Example III

Vehicle Following Example IV

Vehicle Following Example V

Vehicle Changing Lanes Example VI

Yellow Traffic Signal Response IX

Driver Response to an Impact Example X

PRINTING INFORMATION

PATH INTRUSION EXAMPLE 1
We want to estimate the response of a motorcyclist.  One may ask, “Does a motorcyclist’s response take

less time because they do not have the same leg movement as the driver of a car?”  The answer would be both

yes and no.  While the motorcyclist does not have to move their hands or feet very far to brake, their 

search range is typically larger and their response complexity is almost always more complex.  

Therefore, it is best to treat a motorcyclist as you would the driver of a car since the additional 

complexity and the lack of movement time appear to cancel out.

A gray pickup drives north out of a side road and into the path of a westbound motorcyclist.  
The motorcyclist was traveling west at a speed of 42 fps and skidded at 10 feet before impact (.4 factor).
The pick up rolled through the intersection at 5 fps and accelerated at a rate (factor) of 0.15 for the next 40.9 feet.
The driver of the gray pick up looked right, then left before starting forward.
The sight line was limited to 135 feet due to traffic 

Using DRIVE3 

After opening DRIVE3 - click on the term "DRIVE3" 

Then select "Path Intrusion (Side)"

(because the intruder or "target" or "hazard" is emerging from the side of the primary driver (the supposed responder).

If DRIVE3 is not set to the unit of measure you wish, Go to "Setup"

Click on DRIVE3 and selects the unit of measure you wish to work with.  In this example, feet per second.

Then click on "Accept"

Motorcyclist’s Response?
Transition = 3			Anticipation = 5
Experiment type = 4			Driving = 1
Daylight (1)			Urban (2)
Intersection (2)			Single stimuli
Press Eccentricity “Compute”	Primary = 134.355, Intruder = 30.7 = 12.8

Recall here that the pickup moved 40.9 feet, but the front of the pick up was only 30.7 feet left 

from the supposed RESPONDER'S EYES when the intrusion began.

The left side of the screen is the entries and the right side of the screen is

the output.  The Driver Response Equation (DRT) result is 1575 ms. Or 1.6 seconds based 

upon the equations published by SAE in 2003 and 1407 ms or 1.4 seconds based upon the equations that are based upon 

the additional data that has been collected since (and published in 2005 and in press).

Since this was a response to a vehicle, we look at the Adjustment-to-Baseline results from vehicle studies.

The average adjusted response time to studies 3, 4 and 5 is 1.411 seconds and when

we consider both the adjustment-to-Baseline and the DRT equation we have an

"Overall Average" (DRT equation and Adjustment to Baseline) is 1.4 seconds.  

The Standard Precision Range in this case would be 493 ms or 0.5 seconds.  This means that 70% of INDIVIDUALS

will respond within 0.9 and 1.9 seconds under the circumstances you defined.

The user must understand the difference between the accuracy with individuals and the accuracy of the equations generally.

We cannot predict the response time of someone who intentionally crashes or who exercises no care or attention.

However, when averaged, DRIVE3 has consistently (100% to date) predicted the response time for given scenarios within

0.4 seconds.  The results of DRIVE3 should be used as a comparison tool after the crash has been reconstructed.

In that way the analyst may compare the actual response to the average response for a given scenario which

will allow the analyst to offer a conclusion regarding whether the response was above or below average to to what extent.

DRIVE3 will typically round down, however the actual response time is equally

likely to be anywhere within the range of plus or minus 493 ms (which has captured

68.4% of the real life responders to date).  This means that 85% of all drivers will

likely respond faster than 1903 ms (1410 ms Overall + 493 ms Std Precision range).  

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PATH INTRUSION EXAMPLE II
We would like to estimate the response time of the white vehicle in the figure below.

A white Jeep drives east.  A red car stops and then turns into the path of an eastbound

driver at NIGHT.  
The driver of the eastbound white car was traveling at a constant speed of 17.56 km/h

before impact. The red car was initially stopped (initial speed =0) facing the White

Jeep before turning into the intersection (.24 factor) and accelerated forward 7.62 m (25')

and laterally 5.245 m (17.21').  Drive3 assumes that the vehicle drove the arc of the curve defined by

the middle ordinate (lateral distance) and the chord (2 x the linear distance) which equals an arc

length of 11.98 m and an Approach Angle  of 34.5 degrees.  The sight line was limited to 150 m due to a knoll in the road.

Red Car Driver’s Response?
Transition = 3
Anticipation = 5
Experiment type = 4	
Driving = 1
Daylight (2/night)
Urban (2)
Intersection (2)	
Single stimuli
Press Eccentricity “Compute”
Offset Distance (Intruder) = 1.22 m (4')

Linear Distance (Primary) = 15.561 m (This is obtained from the distance of the primary at the start of the intrusion

on the right side of the screen) = 4.4 deg.

The left side of the screen is the entries and the right side of the screen is the output.

The Driver Response Equation result is 1543 ms. or 1.5 seconds.  Since this was a response to a vehicle, 

we look at the Adjustment-to-Baseline results from vehicle studies.  The average adjusted response time

to studies 3, 4 and 5 is 1.788 seconds and when we consider both the adjustment-to-Baseline and the DRT

equation we have an estimated time of 1.666 seconds.  

 The maximum time before the response is the time from when the hazard was first perceivable until the

point that the vehicle first responded (or until impact).

Tip - if the time and distance results do not show, enter a deceleration factor even if the vehicle did

not skid or change speed before impact.

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PATH INTRUSION EXAMPLE III

We would like to estimate the response time of the eastbound red vehicle in the figure

below (assuming north is up).  Another vehicle just passed a pedestrian who was stopped

at the centerline and was attempting to cross from north to south at NIGHT.  

The driver of the eastbound red car (headlight height of 25 inches) was traveling at a constant speed of 40 mph (64.4 km/h) before

impact.  The driver claims that his foot was on the brake pedal because he was traveling

down a steep grade. (Adjustment of ~ –400 ms).  The centerline is 4'(1.21 m) to the left

of the driver’s position.  The pedestrian is walking at an average speed of 3 mph(4.8 km/h).  

The pedestrian was wearing dark clothing on this unlighted road.

The pedestrian did not contrast from the background very well.  If this pedestrian was

not easily identifiable as an immediate hazard, then no driver response time should be

applied.  It is not possible to "perceive" something as an immediate hazard if you cannot

detect it or do not know what it is (is most cases).  Please read the IN CAR CREEDS acronym

under the DRIVE3 Information drop down list.

Using DRIVE3 

After opening DRIVE3 - click on the term "DRIVE3" 

Then select "Path Intrusion (Side)"

(because the intruder or "target" or "hazard" is emerging from the side of the primary driver (the supposed responder).

If DRIVE3 is not set to the unit of measure you wish, Go to "Setup"

Click on DRIVE3 and selects the unit of measure you wish to work with.  In this example, miles per hour.

Then click on "Accept"

For the sake of this calculation however, lets assume this was a lighted road and the

pedestrian was easily identifiable as an immediate hazard (assuming that the driver

was not looking directly in that direction) and no disabling glare or adaptation problems

existed for the driver.

The pedestrian was crossing at a mid block location (not at an intersection or curve)
The sight line was limited to 500 feet due to a knoll in the road (in daylight)

Red Car Driver’s Response?
Transition = 3	Anticipation = 5
Experiment type = 4
Driving = 1	Daylight (2/night)
Urban (2)	Topography Straight (1)
Single stimuli	
Calculate Eccentricity at the start of the intrusion by pressing “Compute”  - 

	Intruder = 4 (1.21 m) 

	Enter Primary = 53.33' (16.255 m) (Start of intrusion distance from the right), 

	= 4.289 deg.

Adjustment –400 ms (leg hovering over brake)

The left side of the screen is the entries and the right side of the screen is the output. 

The Driver Response Estimation (DRT) equation results result is 1869 ms. or 1.9 seconds.

Since this was a response to a pedestrian, we look at the Adjustment-to-Baseline results from vehicle studies.

The average adjusted response time to studies 1, 2, & 9 is 1984 ms and when we consider both the 

adjustment-to-Baseline and the DRT equation we have an estimated time of 1.926 seconds.  

In this instance, an adjustment to account for the reduction of leg movement time and vehicle latency 

was entered.

Be prepared in this case to prove that the pedestrian would be EASILY identifiable as an IMMEDIATE hazard.  If either is 

not true, then this calculation would have no relevance.  Therefore, the analyst must establish an objective threshold at which

the pedestrian could have been perceived by most drivers.

DRIVE3 offers the Twilight Distance Method to calculate the point at which the headlights will likely illuminate ahead up to 

0.3 foot candles (which is the approximate ambient light at Twilight).  Twilight (the end of dusk) has been recognized as the time at which outdoor

activities can no longer be performed effectively.

To utilize the Twilight Distance Calculation, click on the light blue TDM button.  Enter the light threshold (0.3 fc) and the headlight height (25 inches)

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VEHICLE FOLLOWING EXAMPLE IV

DRIVE3 should automatically calculate headway to be 3.57 s., but the user has the option 

to override this entry.  DRIVE3 assumes that the driver has both steering and braking as 

available avoidance options (more options would cause an increase in response time).

 
Red Car Driver’s Response?

Transition = 3		Experiment type = 4	  	Driving = 1
Daylight (1.5/dusk)		Highway (3)		Straight (1)
Single stimuli			

Note that headway when the relative velocity threshold [0.006 radians/sec] is met

is given to the right (3.57 sec).  Note if you enter the headway manually, the word "Headway" will turn red 

and indicate that there was a manual entry.  If you wish to again have DRIVE3 calculate

the headway at the RSAV threshold, then clear the headway box and press enter and headway will again be automatically calculated.

To obtain the eccentricity when the Subtended angular velocity threshold is met.

Press Eccentricity “Compute”
Primary (from the right side of the screen) = 314.64' (65.73 m), Intruder = 0 = 0 deg.  (The bus is straight ahead)

The sight line is 2500' (762 m).

The left side of the screen is the entries and the right side of the screen is the output.  The results show that half of all drivers will

perceive an immediate hazard ahead when 314.64 feet (3.57 sec) away from the rear of the lead vehicle.  From that distance, the average

perception-response time is 1.9 seconds.  Therefore, the average driver's vehicle will begin its maneuver 144 feet before impact (plus or minus the range).

Therefore, DRIVE3  ALLOWS FOR A DIRECT COMPARISON WITH SCENE EVIDENCE.  If the driver did not begin their response 

earlier than 75 feet (143.64' - 68.4') before impact, then that driver responded slower than 85 percent of all drivers in research and real life

situations that were similar to the situation entered.

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VEHICLE FOLLOWING EXAMPLE V Intersection

 
Same situation as above, but this time the lead vehicle stops for an an red traffic signal

at an intersection.  Therefore, change the topography to "Intersection" - 

In vehicle following situations, response times increase as headway increases, 

except when approaching a red traffic signal or a visual cue

that allows a following driver to see that the lead vehicle is not moving

as expected (signs and flashing lights alone may not be effective in many situations).

In these circumstances, research has shown that the headway term is no longer a variable that

is associated with changing response times and if a nominal 1.5 second headway is entered, 

the average response times can be estimated very well.

The left side of the screen is the entries and the right side of the screen is the output.

The Normal Response Time is 1.069 seconds (it is best to report response times to the tenths of a second, such as 1.1 seconds).  DRIVE3 will typically

round down, however the actual response time is equally likely to be anywhere within the range of plus

or minus 427 ms (less than one-half second).  More than 90% of the real life responders to date have fallen

within the precision range of the estimated response time.

This means that 95% of all drivers will likely respond faster than 1.5 (1.069 + 0.427) seconds in this type scenario.

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Example VI: VEHICLE CHANGING LANES

We would like to estimate the response time of the red vehicle in the figure below.

A tan car is changing lanes into the path of the red car from the area 

just in front of the red car driver’s “A” pillar from the driver's perspective

(approximately 20 degrees).  

The collision occurred at noon.
The driver of the eastbound red car was traveling at a constant speed of 96 fps 

(105.33 Km/h) before impact.

The gray car slowed as it moved into the path of the red car.
The driver of the red car applied the brake and skidded 10' (3.05 m)

(0.7 deceleration).

 
The gray car started from the left lane (one lane over).

Red Car Driver’s Response?
Transition = 3
Anticipation = 5
Experiment type = 4	
Driving = 1
Daylight (1)
Highway (3)
Straight (1)	
Single stimuli
Eccentricity = 20 degrees

The left side of the screen is the entries and the right side of the screen is the

output.  The Driver Response Equation result is 1016 ms. or 1.0 seconds.  DRIVE3 will

typically round down, however the actual response time is equally likely to be anywhere

within the range of plus or minus 305 ms (0.3 s).  In research, the actual response

time fell within the range more than 67.6% of the time. This means that 85% of all 

drivers have responded faster than 1322 ms or 1.3 s. (1017 + 305).

Since this was a response to a vehicle, we look at the Adjustment-to-Baseline results

from vehicle studies.  The average adjusted response time to studies 1, 2, & 3 is 1.0

seconds and when we consider both the adjustment-to-Baseline and the DRT equation we

have an estimated time of 1.0 seconds and a range of 0.3 second.   Also note in the 

time and distance calculations that the “average” driver would have started the 

perception process approximately 1.1 seconds before impact (based upon these entries)

and would have been approximately 107' (32.81 m) from impact.

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Yellow Traffic Signal Response IX