1. Given a Traffic light control system with four driving ways and one lane on each side, provided safety considerations. Let D be the safe distance for a car to press break pedal, if a car breaks in a shorter distance that D, there is possibility to cross the red light. A car needs to stop before the sign of S2, S4, S6, S8 (see the figure below). In the following figure, the circle with 3 dots represents traffic light. The dash line splits the road for two driving directions N-S, S-N, and E-W, W-E. Two fundamental rules:
   1. Each car must stop at or before sign of S2, S4, S6, or S8 when red lights.
   2. In addition, a car making turn cannot hit or collide any other car(s), no matter other car is moving or stops.

Your task is to:

• model the system by using correct UML notation.
• point out weaknesses of the system, and describe how the system could be improved to be safer.