Quiz #8

[John QPE]

The passing sight distance for a design speed of 70 mph on a two lane roadway, assuming the passed vehicle is traveling at 58 mph is most nearly:

A. 2480 ft

B. 2285 ft

C. 1200 ft

D. 2135 ft

 

[ptatohed]

Too easy, will refrain from answering and give others a chance first.

P.S. JQ, to be like NCEES, the units should be in the question, not the answers.

 

[John QPE]

Too easy, will refrain from answering and give others a chance first.

P.S. JQ, to be like NCEES, the units should be in the question, not the answers.

I will take the units under advisement. The point of this quiz is to prove an important point. Answer this question using an older GDHS

 

[ptatohed]

Too easy, will refrain from answering and give others a chance first.

P.S. JQ, to be like NCEES, the units should be in the question, not the answers.

I will take the units under advisement. The point of this quiz is to prove an important point. Answer this question using an older GDHS

Hmmm.... my 5th ed GDHS is at home. But I think I know what you mean. There used to be various distances making up the total passing maneuver. Like d1 + d2 + d3.... Now, in the 6th ed GDHS, it's just one table only, right?

 

[John QPE]

OK ... I will spill the beans, as the importance of this is to hammer home the idea of going in with the current NCEES design criteria.

5th Edition does have a table for d1 + d2 + d3

However, they do have a table similar to what is in the 6th Edition (Exhibit 3-7, page 124): Which states that for a design speed of 70 mph, passed vehicle = 54 mph and passing vehicle = 64 mph the passing sight distance = 2,480 feet.

If you look at the 6th Edition, Table 3-4, page 3-9 the passing sight distance for the parameters in this problem = 1,200 feet.

I caught this yesterday, and figured I'd post it so hopefully it helps someone out. I just checked the 1990 GDHS and they have it as 2,500 feet.

And I guess my follow-up question is how the heck did the required sight distance get reduced by more than half?

 

[ptatohed]

You spilled the beans after only 6 hours? lol

You make a good point but, other than this one very good example, I haven't found huge differences b/t the 5th and 6th edition GDHSs, have you? I think the big change was with the HCM (2000 --> 2010). Make sure you have the latest HCM!

I caught my friend using the CERM13 for all his Highway Capicity stuff and I'm like "Dude! The C13 is based on the HCM 2000! Use the HCM 2010, not the CERM!!!"

 

[John QPE]

I haven't found major differences in the GDHS yet, but I haven't been really comparing either. I caught this as I was using an old Mansour book....I have to buy the new ones tomorrow.

I have the 2010 HCM as well, but I am really going to be leaning on the books geared for this exam (Mansour and some Testmasters notes) to hopefully summarize all the tables, charts, design values, etc ...