Figure 4-77 shows the intersection of a main highway with a secondary access road. Vehicle-detection sensors are placed along lanes C and D (main road) and lanes A and B (access road). These sensor outputs are LOW (0) when no vehicle is present and HIGH (1) when a vehicle is present. The intersection traffic light is to be controlled according to the following logic:

1. The east-west (E-W) traffic light will be green whenever both lanes C and D are occupied.

2. The E-W light will be green whenever either C or D is occupied but lanes A and B are not both occupied.

3. The north-south (N-S) light will be green whenever both lanes A and B are occupied but C and D are not both occupied.

4. The N-S light will also be green when either A or B is occupied while C and D are both vacant.

5. The E-W light will be green when no vehicles are present.

Using the sensor outputs A, B, C, and D as inputs, design a logic circuit to control the traffic light. There should be two outputs, N-S and E-W, that go HIGH when the corresponding light is to be green. Simplify the circuit as much as possible and show all steps.

Figure 4-77

Transcribed Image Text:

D A 1 B W C N S E