Control Consistency Checking Using Rules

Drivers expect the controls on all of the roads entering an intersection to be consistent. That is, when drivers see a green light they expect that cross traffic also has a traffic light (and that it is red). We used rules to insure that identified controls were consistent at segment connections. Roads are broken into segments in the digital road map. The points at which road segments connect are called nodes. Nodes typically indicate either an intersection or the continuation of a road. We wrote a set of rules for intersections which also encompasses continuations.

Note that there are some situations, such as that shown in Figure 3, where more than one node in the digital map may correspond to what most drivers would consider a single intersection. These intersections can produce data that violate our rules. These intersections are indicated by short segments in the digital road map. We did not use segment data from intersections with short segments during training as discussed in §2.1.2.

  

Figure 3: Normally, a traffic light at an intersection will correspond to a single node in a digital map as in (A). However, there are some cases where a single intersection may be covered by more than one node as in (B). Correctly assigning the traffic light to the road segments can lead to intersections which violate the rules used by the system.

Segments for intersections that violate the rules below are eliminated by the post processor. We assume that any type of control may be used at any intersection.