CLD Traffic light

[jyang72211]

Hi all,

I have a timing question on the sample CLD traffic light exam (see attachment).  I am seeing a possible discrepency between the spec and the solution. 

On the spec, it says that the duration for each type of light is as follow:

Red: 4sec

Yellow: 2sec

Green: 4sec

However, if you look at the sample solution provided, you will see that the red light will light for 6 second.  Doesn't that exceed the spec?  Anybody has a better (more accurate) solution than provided?

Thanks!

Yik

[pjr1121]

Hello Yik,

If you look at the specification, the sequence is listed as Green, Yellow, Red, Red.  This second Red is necessary to prevent all lanes of traffic from proceeding at once.

If you only keep the Red light on for 4 seconds, the East and West bound traffic will recieve a Green light while the North and South bound lights have just changed from Green to Yellow, resulting a traffic light which does not operate correctly.

The "8" seconds of Red light on will also create a time period where all lights are Red, allowing any slow cars to exit the intersection.