Easiest way is to use formula give in Traffic Engineering Handbook, Pg: 332How would you answer this question:
You are in the right direction. I have the answer but it does not make sense (so far) for me. How did you know about that formula? I looked in the index but couldnt find it. The solution also involves deceleration length. I didn't include the answer bc I want to know if it is possible to get it with the HCM or Green Book instead.Easiest way is to use formula give in Traffic Engineering Handbook, Pg: 332How would you answer this question:
L = VK25(1+p)/Nc
v= peak 15-min flow rate
K = constant to reflact random arrival of vehicle, usually 2
p = percent trucks
Nc = no. of cycle per hour
= 300*2*25 (1+0.1)/40
Answer is B = 413 ft
We have some left turn lanes around that are two or three wide and over a quarter mile long...I would hope that even if the formula answer gave 1000' that ncees wouldn't have that as an answer or even a question, cause there aren't any 1000' left turn lanes around....
Unfortunately, there is no model for idiocy - there is a dire need for such models in the DC areaOn a similar topic, do traffic models use vehicles that during slow-downs, will merge into the on-ramp of a highway just to pass a few cars, therefore slowing down traffic more, causing more people to get into the on-ramp to cut back in?
miloc,Thanks for all your input guys. I did ask to the senior traffic engineer in my office about why and how to find the equation and table in the IE traffic engineering handbook, the answer "It's something that you have to know", as simple as that. P.S. there's a little mistake in the solution regarding the table (or isn't it?) the figure mentioned is for RIGHT-TURN deceleration bay, the question asks for LEFT-TURN.
p.s. I couldnt find the option to upload an image. I'm pasting the solution:
See Figure 10-15 in Traffic Engineering Handbook by ITE
STEP 1 - First determine the required deceleration length (d2+d3) using Table 10-7A
of ITE Traffic Engineering Handbook
Deceleration length for 50 mph speed = 565 ft
STEP 2 - Compute storage length (d4) using left-turn storage length equation
25(L =VK 1+ p) / Nc = 300*2*25(1+0.1)/40 = 412.50 ft
STEP 3 - Total left-turn bay length = 565+412.5 = 977.50 ft
Answer C
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