A Plan to Get to Evanston

This is the plan shown in Figure 3 and discussed in Section 2.3.2. Note the decision-step with a single active decision-rule. This is the situation discussed in the comments on one-sided contingencies in Section 6.5: the route using Western is quicker when it is clear, while the Ashland route is slower but always possible.

Initial:       When [TRAFFIC0S: GOOD] (NOT (TRAFFIC-BAD))
               When [TRAFFIC0S: BAD] (TRAFFIC-BAD)
               (AND (AT START) (ROAD WESTERN) (ROAD BELMONT) (ROAD ASHLAND))

Step  1 (4): (GO-TO-WESTERN-AT-BELMONT)           YES: [TRAFFIC0S: GOOD BAD]
               (AND (NOT (AT START)) (ON WESTERN) (ON BELMONT))
                  0 -> (AT START)

Step  2 (3): (CHECK-TRAFFIC-ON-WESTERN)
               (KNOW-IF (TRAFFIC-BAD))
                  1 -> (ON WESTERN)

Step  3 (2): (DECIDE TRAFFIC0S)
               (and (NOT (TRAFFIC-BAD))
                    T                ) => [TRAFFIC0S: GOOD]
               (and T                ) => [TRAFFIC0S: BAD]
                  2 -> (KNOW-IF (TRAFFIC-BAD))

Step  4 (6): (TAKE-BELMONT)                       YES: [TRAFFIC0S: BAD]
                                                  NO : [TRAFFIC0S: GOOD]
               (AND (NOT (ON WESTERN)) (ON ASHLAND))
                  1 -> (ON BELMONT)

Step  5 (5): (TAKE-ASHLAND)                       YES: [TRAFFIC0S: BAD]
                                                  NO : [TRAFFIC0S: GOOD]
               (AT EVANSTON)
                  4 -> (ON ASHLAND)               NO : [TRAFFIC0S: GOOD]

Step  6 (1): (TAKE-WESTERN)                       YES: [TRAFFIC0S: GOOD]
                                                  NO : [TRAFFIC0S: BAD]
               (AT EVANSTON)
                  1 -> (ON WESTERN)               NO : [TRAFFIC0S: BAD]
                  0 -> (NOT (TRAFFIC-BAD))        NO : [TRAFFIC0S: BAD]

Goal:        (AT EVANSTON)

             GOAL                                 YES: [TRAFFIC0S: BAD]
                  5 -> (AT EVANSTON)              NO : [TRAFFIC0S: GOOD]

             GOAL                                 YES: [TRAFFIC0S: GOOD]
                  6 -> (AT EVANSTON)              NO : [TRAFFIC0S: BAD]

Complete!