Que dissipation- 6 min solution & Goswami

[Predgw]

Problem #70 of 6 min solution- transportation. Two lans of a freeway have a capacity of 4200vph. Normal flow is 3100vph. An accident occurs and blocks traffic for 10 minutes. After 10 mins, both lanes are open back up. How long does it take for traffic to break up?

Convert flow to vehicles per minute, write equation. I got 51.67(10) + 51.67t= 70t answer 28 mins. 6 min solutions agrees.

Goswami all in one, page 688 and 689, example 401.5 Same problem slightly different numbers. The accident is 15 minutes, the flows are different .

However, the book sets total time for arrivals at T, then sets total time for departures at T-15 The book then plugs T-15 into the equation and comes up with T as 55 minutes. When I write the equation like I did for the 6 min solution I get the time as 40 minutes. It appears the Goswami book is addiing the accident time into the answer by not subtracting the 15 mins. The equation for departure is T-15, yet he solves for T and states that to be the answer.

This seems like an easy errata, a simple step was missed, however I cant find an errata for it.

Any thoughts?

Thanks

 

[ptatohed]

Crud, I don't have any of my books (All-In-One, 6-Mins) with me, but I totally remember this and I totally remember making notes in one that the other was correct. I think it was the 6-Mins I agreed with and the AI1 I think needed a correction. Sorry, can't help more.