STISIM Drive (SDL) - SL - Signal Light

Display a traffic signal light. The lights are controlled with specified parameters. This option does not display an intersection, that must be done with the I event. When the signal light is red and a driver drives past the signal light, the siren sound effect will be played (if active) and a ticket will be added to the driver’s ticket total. The current status of the lights can be output to the STISIM Drive data file using the BSAV event and therefore the driver’s reactions to the signal light can be measured. Additionally, data is included in the STISIM Drive data file that tells you how many of the signal lights that the driver stopped at. A stop is defined as a signal light where the light changed from red to green before the driver went through.

The lateral position of the stop lights is based on the sign post distance defined in the program's configuration options.

EVENT PARAMETERS:

PARAMETER 1:

The longitudinal distance, in feet, that the signal is away from the driver when the signal initially appears. Because the roadway is more flexible in STISIM Drive than it was in the DOS version of STISIM, we have added some additional functionality to this parameter. If this parameter is specified as a negative number, then the program will automatically figure out (to the best of its knowledge based on the current roadway) where the signal lights will be placed. Otherwise, it will act as specified.

This option was added because it is now easy to have the roadway transition from a set number of lanes to another set number of lanes and if you are trying to use a PDE that has signal lights in it and the roadway is a different size, you may have trouble. The longitudinal distance is still the same, it just has a minus sign (-) in front of it. If you are using this option, you must make sure that the signal light event lines up with the intersection event, otherwise the lights will be mis-aligned. For example if you have an intersection that is 1200 feet away, you want the signal light event to be -1200 feet away.

PARAMETER 2:

The amount of time, in seconds, that the driver is away from a green traffic light when it changes to yellow. This time is based on the driver's velocity when the event first begins.

PARAMETER 3:

The length of time, in seconds, that the yellow light remains on.

PARAMETER 4:

The length of time, in seconds, that the red light remains on.

PARAMETER 5:

Initial light setting:

0 -    Green light

1 -    Yellow light

2 -  Red light

PARAMETER 6:

Distance from the traffic signal location to the "true" limit line, in feet. It is advisable to set the signal light at the back of the intersection so that if the driver stops, they can still see when the signal light turns green. However this can cause problems when issuing tickets for running the red light, because the ticket is issued based on the signal light’s location. Because of this problem, an additional parameter has been included that allows you to specify where the limit line will occur with respect to the signal light. If the driver does not cross the limit line before the light turns red, then a ticket will be issued, otherwise no ticket will be issued. Specifying this parameter with a negative value will place the limit line in front of the signal light, a positive value will place it behind (farther down the road) the signal light.

PARAMETER 7:

Signal light type. Allowable types are:

1 -    On a post at the four corners of the intersection

2 -    Overhanging the roadway 15 feet at the four corners of the intersection.

3 -  Overhanging the roadway 25 feet at the four corners of the intersection.

PARAMETER 8:

Signal light sequence (if not specified it defaults to the United States sequence):

1 -    United States: Green, Amber, Red, Green

2 -  Generic European: Green, Amber, Red, Red/Amber, Green

EXAMPLE:

1000,SL,1000,5,3,10,0,-15,1
1000,SL,-1200,5,3,10,0,-15,1
2200,I,0,0,1

STISIM Drive has a multitude of events that can be used to measure a driver’s reaction to different tasks. This event is another. The SL event can be configured so that the driver must make critical stopping decisions or they will run a red light. Outputting the current light position, the run time, accelerations, and speed will allow you to asses the driver’s response to the SL event.

In the first example shown, the signal light will appear after the driver has traveled 1000 feet down the road (1000,SL). When the signal light is initially displayed it will be 1000 feet away from the driver. As the driver approaches the signal light, STISIM Drive will monitor the driver’s velocity and compute the time it will take the driver to reach the signal light. When the driver is within 5 seconds of the signal light, the light will turn from green to yellow. The light will then stay yellow for a total of 3 seconds at which time it will turn to red. The light will remain red for a total of 10 seconds and then turn back to green. The initial light that will be displayed is green (0), and the limit line for the signal light will be 15 (-15) feet in front of the light. If the driver runs the red light, they will be issued a ticket and the police siren will be played if it is activated. The light will be displayed on a post at each corner of the intersection.

In the second example, the signal light will appear relative to the intersection that is specified in the second line. This is because we put a minus sign in front of the longitudinal distance (-1200). This means that no matter what the roadway sizing is (number of lanes and lane widths) the lights will be placed properly in the scene. This will work correctly because the center of the intersection (2200 feet) and the distance of the signal light event (1000 start distance + 1200 longitudinal distance = 2200 feet) match, otherwise there would be an offset based on the offset between the 2 events. The signal light that is displayed will be the same as the first example.