Collision Avoidance Vehicle Following
Overview: Computes
speed, time and distance at which a deceleration or evasive maneuver must begin
to match the speed of the accelerating,
decelerating or constant-velocity lead vehicle.
Entry into Module:
This module of the program is normally entered by clicking
on the REC-TEC block in the upper left of the REC-TEC Window
causing the drop-down menu to appear.
Place the cursor on the Collision Avoidance block and click on Vehicle
Following on the sub-menu to initiate this module.
Under certain circumstances, the user may choose to use the
Files block instead of the drop-down menu approach. Selecting any file with a .CAF
extension in the Dialog box accessed from either the Open Single File
or Open Multiple Files block opens this module.
Selecting AutoLoad [ON] from either the Setup
Menu or the AutoLoad Icon on the upper right side (third line) of
the REC-TEC Window automatically loads the scenario that was on the screen
when the module was closed, either individually, or when the program was
closed. With AutoLoad [OFF] on
the main REC-TEC Window, modules will start without loading a
file.
Data Entry:
This module contains the following data entry blocks within
the leftmost frame:
·
V1 Speed (I) Following
(Bullet) Vehicle at Start of Maneuver
·
V2 Speed (I) Leading
(Target) Vehicle at Start of Maneuver
·
RSAVT (Rads/Sec)
Relative Subtended Angular Velocity Threshold in Radians per Second
·
V2 Dimension Height or
Width Cue for Subtended Angular Rate Change Computation (Height/Width of
Trailer or Distance between tail lights
·
Min Lat. Dist. Minimum
Lateral Distance (Turn / Lane Change)
·
Reaction Time Time
before V1 reacts to V2 maneuvers
·
Safe Distance Separation
Distance Between Vehicles at Speed match
·
Acceleration (+/-) (V1)
Acceleration Factor if V1 Accelerating (+/-) prior to entering Max rate
Deceleration
·
Lateral Accel. (V1)
Lateral (Y-Axis) Acceleration Factor - Required
·
Acceleration (V2)
Acceleration Factor (X-Axis) if V2 Accelerating (+/-)
·
Maximum Decel. (g)
Maximum Available Deceleration (g)
Entry of Data is sufficient to generate a solution and
causes output information to appear in the Output frame. As the input data is changed, the output data
is automatically updated without the need to tell the program to update the
output. Error Message will be displayed
if no Contact is possible for Data entered.
Output:
The output from this module consists of the repeated input
variables entered into the left Input frame expressed in the primary and
secondary configurations.
Lateral Distance/Acceleration Data enables computations on the right side of the screen
showing Turn and Lane Change information.
The top frame heading shows the entered lateral
distance. The next two lines show the Maximum
Lateral Distance along the YAxis that can be reached if the maneuver is
started from the Slide-to-Stop Distance on the X-Axis for each of the maneuvers
involved.
The left - Turn: (Lateral Distance @ f and V1) and
the right - Lane Change: (Lateral Distance @ f and V1) frames show the
following:
·
Distance(X) - X-Axis distance required for the maneuver
·
Hypotenuse Straight-line distance from the start of the maneuver to
the Y-Axis point at the Lateral Distance
·
Arc Angle The angle or combined angles through which the vehicle
has traveled in the maneuver
·
Arc Radius Radius of the turn(s) required for the maneuver(s)
·
Arc Distance Distance traveled by the vehicles following the arc(s)
required for the maneuver
·
Arc Time Time required for the maneuver if Initial Speed is
maintained
Critical Turnaway is a
Speed at which the Distance Slide-to-Stop and the Distance
required for the Turn (or Lane Change) maneuver are identical. Again, Critical Turnaway is a Speed at
which two distances are identical.
It is similar to a point of no return.
·
Critical Turnaway Distance Distance for both Slide-to-Stop and Distance required
for the Turn (or Lane Change) maneuver
·
Critical Turnaway Time Time required to stop from the Initial Speed
·
Critical Turnaway Speed The Speed at which the Distance Slide-to-Stop and the
Distance required for the Turn (or Lane Change) maneuver are identical
1
V1 Dist Contact (Spd
Match): V1 - Distance to Contact (Spd
Match) from Time Zero (0)
2
V2 Dist (Spd Match)
Contact: V2 - Distance to Contact (Spd
Match) from Time Zero (0)
3
V2 Acc
(+/-) Time: Includes time V2 is
Accelerating (+/-) before V1 begins Decelerating
6
V1 Maximum f: Maximum Deceleration Factor (g)
7
V1 Max Dec Dist.:
Distance Required to match V2 Speed - Maximum Deceleration (g)
8
V1 Max Dec Time:
Time Required to match V2 Speed -
Maximum Deceleration (g)
12 Event Max Time: Maximum Time from Time Zero (0)
Options:
Several Command Buttons appear in a frame located at
the lower right corner of the module Window.
The Command Buttons allow the user to engage options including
the option to Open and Save the data required to generate the
scenario shown on the screen at the time the file was saved.
·
Open .CAF File Calls up a Dialog box, which Opens any
pre-existing .CAF file and displays the output results.
·
Save .CAF File Calls up a Dialog box, which Saves data on
the screen to files with any user-selectable filenames. This is independent of the automatic saving
as LastFile.CAF of the data at the close of this module or the close
of the program.
·
Animation The display shows the Deceleration curve in the upper block
and the Turn (upper middle block) and Lane Change (lower middle block).
Time (top scale) and Distance (bottom scale) is shown for all three
curves. Animation may be stopped and
resumed using the mouse or the spacebar.
[Esc] to Exit
·
Tables Tables show f required to clear (Match V2 Speed) and
Closing Speed at Maximum Available Deceleration from Time frame or the
Subtended Angle (Radians) and Rate of Change of the Subtended Angel in
Radians/second. Both tables display
Time in user selectable increment to Point of Contact. Table data includes instantaneous speeds for
V1, V2, Closing Speed, required distance for Turn and Lane Change, Separation
Distance between Vehicles and Time to Impact and Distance traveled by V1 and
V2.
·
V1 > TDME and V2 > OMNI
These buttons allow the V1
data to be transferred to Time Distance Multiple Events and the data
from V2 to be transferred to Time Distance OMNI. These automatic transfers allow further
analysis and as a cross check on the math and the graphics.
·
N This button toggles a graphical number pad on the screen
that can be used to enter data into the input boxes without using your keyboard
number pad. This may be useful for
presentations as data entry can be accomplished using a wired/wireless mouse.