Quiz #5

[John QPE]

OK ... shooting from the hip here

Given:

A vehicle traveling North on a road with a 1 percent upgrade approaches a signalized intersection at 25 mph. The East-West cross street contains (4) 11-foot wide lanes, with a 10-foot grass center median. Assuming a deceleration rate of 10.0 ft/sec^2, and a reaction time of 1 second, determine the total clearance interval for the intersection.

A. 3.0 seconds

B. 2.0 seconds

C. 6.0 seconds

D. 5.0 seconds

 

[ptatohed]

My friend and I worked this after work today. We get answer D.

 

[John QPE]

D is correct.

4.79 seconds. Remember to round up to the nearest 0.5 seconds

 

[Schiefe4]

What reference material can I use to solve this problem?

 

[John QPE]

HCM 2010, page 18-67

 

[smilestar]

I am not getting 4.79, please let me know what I am doing wrong. Below is my calc

Y= t + V(2a+2Gg) = 2.2

R= W+L /V = (54+20)/25 = 2.96

Y+R= 5.16

where L = length of the vehicle, assume 20 ft

 

[John QPE]

Did we jack this problem up?? Possibly ...

Y = tr + { V/(2a + 2gG)}

Y = 1 sec + {36.75 ft/sec} / {2 (10 ft/sec2) + 2(32.2 ft/sec2)(.01)} = 2.78

R = (54 ft + 20 ft) / 36.75 ft/sec = 2.01 sec

Yi = Y + R

Yi + 4.79 ....... then round up to 5.0 seconds

Remember you must convert mph to fps for this problem.

 

[smilestar]

ohh great ya I need to remember that 2 days before the exam.

 

[mikeyliv]

HCM 18-67 2010? I dont see it.

 

[mikeyliv]

HCM 18-67 2010? I dont see it. Am i missing something here?

 

[John QPE]

Hmmmm .... that page is pedestrian green time. Not sure what I was thinking there. I don't have time to go looking now, but I'm sure it's in chapter 18 somewhere....but the equations you need for yellow and red clearance are right above.

 

[John QPE]

As a follow up ... these equations come from the ITE Traffic Engineering Handbook.

I can not find them in the HCM, which really surprises me.

 

[ptatohed]

As a follow up ... these equations come from the ITE Traffic Engineering Handbook.

I can not find them in the HCM, which really surprises me.

I think they are in the NCEES FE Reference Handbook too. http://ncees.org/exams/study-materials/download-fe-supplied-reference-handbook/

The ITE TEH was on the NCEES list of references a few years ago.