HCM: Signalized Int. - Lane Width Assumptions

[emmmsterder]

So I am going through some of the problems in the HCM and am working on Ch. 16 - Signalized Intersection, Example 1. For 3rd Street (2 lanes, one in each direction) they assumed the crosswalk length was 44 ft, and Main Street (four lanes, two in each direction) as 30 feet. Does anyone know where these numbers came from? On the diagram of p. 16-42 it says that the lanes across Main Street are 11' each and the lanes across Third Street are 15' each. I can do the math, but I dont know where they came up with 11' feet and 15' lanes.

In the other Examples, they give the lengths of the crosswalk but even in the diagrams they assume there are medians.

Is there a way to determine the lane widths or do they just assume? I am confused on that.

 

[VA_NowPE]

So I am going through some of the problems in the HCM and am working on Ch. 16 - Signalized Intersection, Example 1. For 3rd Street (2 lanes, one in each direction) they assumed the crosswalk length was 44 ft, and Main Street (four lanes, two in each direction) as 30 feet. Does anyone know where these numbers came from? On the diagram of p. 16-42 it says that the lanes across Main Street are 11' each and the lanes across Third Street are 15' each. I can do the math, but I dont know where they came up with 11' feet and 15' lanes.
In the other Examples, they give the lengths of the crosswalk but even in the diagrams they assume there are medians.

Is there a way to determine the lane widths or do they just assume? I am confused on that.

To answer your question they will always tell you what the lane widths are like they do in this example (see the diagram on 16-42 where they graphically drew in the lane widths). There is no way to determine them unless you go out and measure them. On the PE exam they will always provide you with enough information to solve the problem - just look carefully.

 

[Vishal]

To answer your question they will always tell you what the lane widths are like they do in this example (see the diagram on 16-42 where they graphically drew in the lane widths). There is no way to determine them unless you go out and measure them. On the PE exam they will always provide you with enough information to solve the problem - just look carefully.

I second this opinion. The lane widths in general are go from 10' to 12'. If you have some shoulders or a wider for ramp on a freeway then it is possible that the problem will say that the lanes are 15' to 16' wide.

However, it will almost always be mentioned in the problem about the lane widths and any other parameters required to put in the equation. I used the word almost always since there is a possibility that a piece of information is missing, then you can always disputet he problem. A word of caution here... the information is not always explicitly mentioned, sometimes you have to look at the given diagram closely or read the problem statement line by line and collect the information.

Good luck.