Knowledge Base

Article Number: 29 | VC3 | VC4 | Post Date: March, 9 2017 | Last Updated: March, 9 2017

How can I use the auto-driver to set up an intersection collision?

It’s extremely simple to use the auto-driver system to set up a collision in Virtual CRASH. First, we’ll start by importing and scaling this aerial image of our intersection.

Here is our image imported and scaled:

Next, using the line tool, a line is drawn to show the intended trajectory of our first vehicle.

Using the curve tool, the intended trajectory of our second vehicle is created.

Next, the vehicles are placed into the scene. Their initial positions are set randomly atop their intended trajectories, and will be refined later.

The auto-driver is then enabled for our two vehicles.

Now with both vehicles selected, the vehicles are given initial speeds of 35 mph in the dynamics menu.

The driver of the blue vehicle slowed prior to beginning the left turn maneuver. Using the braking fast control icon, we can input a deceleration maneuver as the blue vehicle travels through the left turn lane. Note when the braking fast control icon is touched, a deceleration entry is automatically placed in the sequences menu. The deceleration rate can be fine-tuned either by using the fast control icon, or by specifying a value in the acceleration field. Here a value of about 0.15 g’s was used. The time value of the deleration sequence controls when brake application begins (with a 0.2 second brake lag by default). This time can be adjusted either in the time field in the sequences menu, or by issuing a left-click-and-hold-and-drag on the “I” icon and sliding the vehicle backward or forward along its trajectory. Note, the initial position is adjusted further back in our example below.

Finally, the look ahead time is adjusted to 0.5 seconds so that the blue vehicle follows the auto-driver path more closely. 

Next, reaction and deceleration sequences are added to the red vehicle. Here the reaction sequence entry is used to mark the moment when the blue vehicle begins intruding into the red driver’s lane of travel. 

The deceleration sequence is set to start 0.5 seconds after the reaction sequence (with a default 0.2 second brake lag to go from 0% to the full deceleration rate, linearly interpolated). Recall, the time parameter is the time with respect to the prior sequence entry. One may also use type:distance rather than type:time. 

Finally, the initial position of the red vehicle is fine-tuned using the two-screen display, in order to ensure the area-of-impact is at the passenger side rear axle of the blue vehicle. Since the reaction sequence event time is set with respect to time = 0 seconds (no prior sequence entries), the time parameter does not need to be adjusted for reaction since the moment at which the blue vehicle crosses into the oncoming lane is independent of the initial position of the red vehicle. In addition, the braking input for the red vehicle is set to occur 0.5 seconds after the reaction event, which is also independent of the red vehicle’s initial position. 

The ees object can be selected in order to adjust the collision model parameters such as the coefficient of restitution as needed for your case. Additionally, a user contact can be created to fine-tune the impulse centroid location to further help best match your forensic evidence, as well as to enable deformation. The process of fine-tuning the ees object is the subject of Chapter 12 of the User’s Guide, as well as various Blog posts. 

Tags: auto-driver, setting up a crash, making a collision, drive vehicle on path to crash

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