some question on traffic.

[tsli001]

Hi guys:

I’d just took a online mock test on transportation. And it is not so good. I ‘d had some questions here see anyone can help me on this. 1,Can someone help me on the space-time diagram. Like how to establish? How do I draw the speed on the diagram? How can I find the bandwidth from the diagram? One more thing is the green book, I only got a 2001 green book. Can someone tell me where can I find exhibit 3-32 for superelevation runoff. Cause some one tell me the minimum runoff for a design speed of 60mph is 320ft. I’d just cant find it.

Thank you

tsli

 

[petobe]

Ill take a shot, but I'm not positive what you're asking in either question, so hopefully it helps.

A time-space diagram generally shows the signal phases as a function of time, which is plotted against the distance traveled. Its mostly used to show the relationship between traffic signals and the platoon of vehicles that could travel through the intersections in any given amount of time (green time of the signals, taking offset into account), or the characteristics of traffic entering intersections in a stream. The amount of green time that can be used by a continuously moving platoon (ie, not slowed down by turning traffic, etc) through the intersections is the bandwidth. The speed is simply a function of the distance traveled in the time it takes to travel it (or the slope of the particular line on the diagram).

Take a look at Exhibit 10-1 in the HCM.

As far as the Green book exhibit 3-32... its on page 181 for US units... not sure where you can get it without the book. For a design speed of 60 MPH, 320' is only the correct minimum distance if you are rotating 1 lane with max superelevation (12%).... but it ranges anywhere from 0' to 480 for that speed, depending on the actual variables (lanes rotated and superelevation).

 

[tsli001]

Ill take a shot, but I'm not positive what you're asking in either question, so hopefully it helps.

A time-space diagram generally shows the signal phases as a function of time, which is plotted against the distance traveled. Its mostly used to show the relationship between traffic signals and the platoon of vehicles that could travel through the intersections in any given amount of time (green time of the signals, taking offset into account), or the characteristics of traffic entering intersections in a stream. The amount of green time that can be used by a continuously moving platoon (ie, not slowed down by turning traffic, etc) through the intersections is the bandwidth. The speed is simply a function of the distance traveled in the time it takes to travel it (or the slope of the particular line on the diagram).

Take a look at Exhibit 10-1 in the HCM.

As far as the Green book exhibit 3-32... its on page 181 for US units... not sure where you can get it without the book. For a design speed of 60 MPH, 320' is only the correct minimum distance if you are rotating 1 lane with max superelevation (12%).... but it ranges anywhere from 0' to 480 for that speed, depending on the actual variables (lanes rotated and superelevation).

[/quo]

Ah ok..hank you for you help, I'm just got one more thing would like to ask. I only got 2001 green book, and on p181 is exhibit 3-34 'Desirable lenght of spiral Curve Transition' and can you explain a bit more on ratoting 1 lane with max superelevation, or may be you can direct me to the correct topic so I can read it it up