Specifications

5
Battery Charger—BatteryMinder 12117, $50.00
This charger has a large enough capacity while also providing functions that can enhance
battery life, such as desulfation and over/under charging protection. It has a visual monitor
that tells charge state and quick-connect cords.
Battery Cases—4 Group 27 Battery Boxes, $45.00
These vented boxes are designed to provide good protection from the elements and also
provide mounting straps.
3. DIGITAL VIDEO RECORDING PROCEDURE
In order to simplify the digital video analysis procedures, a standard camera–intersection
configuration was adopted. The standard configuration requires that a single digital video camera
is placed 50 feet from the lane of interest. The camera should be mounted on a secure tripod in
order that the system stays fixed and is not perturbed by small gusts of wind. The camera height
should be set to 4 feet. The rotation of the camera must be set such that the view direction of the
camera is perpendicular to the lane of interest. The camera position parallel to the lane of interest
is unconstrained. For the study of intersections, it was found ideal to position the control device
(e.g., stop sign) approximately in the center of the camera’s field of view. An image taken from
the camera’s point of view in the standard configuration is shown in Figure 3.1 for a non-
signalized four-way stop.
Figure 3.1. Calibration markers placed 10 feet apart
Once a camera is set up in the standard configuration at an intersection, a calibration procedure
must be followed. This procedure allows the digital video analysis to estimate distances in the
scene (in feet) using distances in the images (in pixels). The procedure requires that two planer
markers are placed within the camera’s field of view along the intersection of interest. Each
marker is an 8.5 inch by 11 inch checkerboard pattern printed onto a rigid material and mounted
to a tripod. A checkerboard pattern is used so that the digital video analysis can precisely locate
the marker at the sub-pixel level. The markers must be set up parallel to the lane of interest and
as close as possible to the lane of interest. Although the optimal calibration process would place
the calibration markers in the center of the lane of interest, practically, this can be difficult. It
was found that placing the markers just outside of the lane of interest was sufficient for vehicle
tracking purposes. The distance between the checkerboard centers must be set as close as