help on traffic circle (rotarie, roundabout...)

[Tony C. Tweedale]

i posted the follwing to sci.engr.* and got only 1 response, so i'm trying
all you guys...(remember to e-mail me; i'm not on auto.* or bicycle.*...)

i need information on the design requirements for a traffic circle/roundabout.

the maximum capacity is projected @ 6,000 vehicles/hour and the intersection
has 6 legs (3 streets). the setting is urban/commercial. during rush hours
average speeds are about 20-25 mph until traffic reaches the intersection
("malfunction junction").

i'd like to know what diameter circle is needed. (there's a fair amount of
money for this project through the federal Congestion Mitigation & Air
Quality fund--our city is the only one in our state to be in nonattainment
for carbon monoxide, so we got the entire state's share of the fund.

any other insights appreciated, or any referals to people/literature/discus-
sion groups. i'm no engineer, so no calculus please (algebraic formulas ok).

respond by email to address below as i'm not subscribed to engr.*. thanks,

tony tweedale (internet: es...@selway.umt.edu) tel 406-542-1709
grad, env studies prgm.
rankin hall, u. montana >> 1 planet, 1 experiment, one species <<
missoula mt 59812 (derived from Edmund O. Wilson, biologist)