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From: warren@ihnss.UUCP
Newsgroups: net.auto
Subject: Dim-Bulb traffic designs
Message-ID: <1610@ihnss.UUCP>
Date: Fri, 15-Jul-83 17:19:00 EDT
Article-I.D.: ihnss.1610
Posted: Fri Jul 15 17:19:00 1983
Date-Received: Tue, 19-Jul-83 17:58:37 EDT
Organization: BTL Naperville, Il.
Lines: 55

Since everyone had so much fun with the physics of freeway traffic,
here are three more little mysteries of auto traffic.  This time the
question is why these systems are designed the way they are, which
in each case would seem to lead to more congestion and confusion:

1)	Parking lot funnels.  I have noticed increasingly that
	parking lots for large stores and shopping centers seem to
	be designed to make it difficult to park without first
	passing in front of the store (between the parking area and
	the entrance.)  In some in illinois, you must pass through
	this area at least twice, once to get in and once to get
	out.  This design maximizes the chance for
	vehicle-pedestrian collisions, encourage parking illegally
	near the store, and generally increase congestion.  Why not
	instead have no roadway in front of the stores, only
	turn-around space for going from one parking aisle to the next?
	
2)	Advanced green lights.  I used to see a fair number of
	traffic lights with cycles that gave left-turn cycles to
	cars waiting at the end of the normal green cycle.  Now, I
	rarely see these things that do not give dedicated left-turn
	cycles if a car is waiting at the beginning of the cycle. 
	The difference is that if traffic conditions are light
	enough to permit the left-turners to get through the normal
	cycle, then no special cycle is needed.  The new lights,
	however, give them one anyway, since the decision is made at
	the start of the cycle.  Putting the left-turn cycle at the
	end of the normal green cycle would seem to me to reduce
	congestion (by increasing the proportion of time given to
	through traffic) and would avoid the problem caused by
	several cars trying to make left turns after the light turns
	I don't see why these lights are designed the way they are.
	
3)	Tripped lights.  In several areas of my town, 2-way stop
	signs have been replaced by tripped traffic lights.  The
	effect has not been positive.  On these streets, during most
	of the day traffic on the side street could escape within 30
	seconds.  With the tripped lights, traffic must wait for a
	light cycle, frequently a long time, which then stops all
	traffic on the main street for a considerable period of
	time.  Why doesn't anyone set these things as flashing red
	for the side street, permitting cars to exit, and trip to
	stop the traffic on the main street only after a timeout of
	30 seconds or so?  It seems like a much better solution.
	
Feel free to ignore these questions, but I find them more
interesting than yet another bags vs belts debate, more on radar
detectors, the 55mph limit, big vs small cars, and any of the
numerous other constantly recycled topics.

-- 

	Warren Montgomery
	ihnss!warren
	IH x2494