Responses to "Speed Limits and Stop Lights"

The point:

Speed limits should also be increased on other roads. Slower speed limits on busy high speed highways tend to create an engineering difficulty with syconizing stop lights. If stop lights are synconized by using the speed limit often people will have to stop at the next light when it wasn't engineered that way. If speed limits were raised to the speed of traffic, then this would not be a problem. It also creates a miner hazard in the length yellow lights stay on. (Is this true? I am just speculating here on this whole paragraph. Engineers out there please let me know)

The responses:

From: Sean Morrison
Date: Wed, 4 Oct 1995 16:34:34 -0400

Here in New Orleans the lights are all set completely at random, and
all the yellow lights last different lengths of time.  There is
clearly no science to that.

In Montreal, the lights are set at the legal limit, and yes, even I
followed the limit when that was the case.  This simple point could
save many lives if it were instated in the US.

From: Bob Morrow &th;>
Date: Wed, 11 Oct 1995 00:28:24 -0400

I happen to agree with one person's opinion here about "all-red"
intersections.  We'll make every intersection's lights go all-red
for a few seconds, then a few more, etc.  What will happen is the drivers
will figure this out and simply go when they see the other side
is red.   They will then be cited for running a red light when they had no
reason to sit still.

From: Shawn Holyoak <>
Date: Thu, 5 Oct 1995 19:07:29 -0400 (EDT)

You requested examples of roads that dealt with speed limits and stop 
lights.  Michigan Ave. in running from the west suburbs of Detroit all 
the way into Detroit is a perfect road in this way.  If one drives five 
over ( a speed where most cops will let you alone), one can drive the 20 
or so miles into Detroit stopping only once or twice (even that can be 
avoided if one knows where to speed up slightly!):-).  The great thing 
is, even during rush hour when the road is extremely busy, traffic flows 
wonderfully.  The entire reason for this is that the several cities 
through which Michigan Ave. passes have gotten together and set up a 
reasonable speed limit.  Traffic flows great and I see few accidents.  
(Statistics on accidents would be interesting to see though).

I agree with your basic premises too.  Speed does not kill.  Facts
show that the majority of accidents occur because someone runs a red
light or other brainless maneuver.  Keep up the good work!

From: Angela Leigh Hyrne <>
Date: Sat, 19 Aug 1995 12:49:12 -0400

I am an engineer in the Air Force.  I am currently stationed in Wichita,
KS; where there are seemingly no such thing as traffic engineers.  We
have 25mph and 30mph speed limits through downtown areas with four lanes
of traffic.  This is ludicrous!  Most people drive comfortably at 40mph,
but if you get, and your insurance, are screwed.  Also, for
some stupid reason, there are very few roads with middle turn lanes.
When there does happen to be a middle turn lane, no one knows what it is
for, and therefore, no one uses it.  This is poor planning/engineering!!
It is also a show of the stupidity of the drivers around here.  There is
one, maybe two, streets through downtown Wichita that have synchronized
lights (most of the way, anyway).  Basically, if you are driving at the
posted speed limit, which is 35 on this street, you will catch all but
the last one.  Obviously, someone has a basic understanding of the
concept.  If only the city were smart enough to apply it everywhere else.
Most of the time, the lights seem to be synchronized so that you catch
every light red.  Rumor has it that the city does this to make it look
like Wichita is a thriving metropolis.  Enough complaining.

Yes, lights are supposed to be synchronized so that if you are constantly
doing the speed limit, you should catch them all green.  Yellow lights
are supposed to be timed according to the speed of traffic, (the speed
limit), and the safe stopping distance/time of an automobile; so that no
one has to slam on their brakes in order to stop on time.  The length of
green lights, yellow lights, and the time period where all lights are red
are based on the volume and speed of current traffic, factored with safe
stopping distances, speed, acceleration rates, and human factors such as
recognition times, and impatience (people running through yellow lights),
etc.  These traffic studies should be updated more often!!!  Maybe then
they would notice that the speed limits are set too low.  

From: Matthew T. Russotto <>
Date: Sun, 8 Oct 1995 23:55:58 -0400

In Maryland and Pennsylvania, speed limits on secondary roads are often
as big a joke as the double nickel.  In Maryland, the lights are NOT
synchronized to the limit-- they appear to be synchronized to something
approximating the real traffic speed.  This means that if you do drive
the limit, you'll hit every light.  I originally thought this was
a clever way of making more money for the state, but more likely the
traffic engineers set the lights and the politicians set the limits.
PA doesn't appear to have traffic engineers... this state does stupid
things like setting lights to no cycle and 3rd car detection (so if you're
the only car there, you'll wait indefinitely)

As for yellow and all-red time, there's a basic problem.  The traffic
engineers set them for a certain margin of safety.  Most drivers prefer
a smaller margin of safety, and do so by running the yellows and the
double-reds.  This seems to lead to longer and longer all-red times, which
causes more and more drivers to run them.  This is especially true during
rush hour, when the all-red is mostly unnecessary because no one is
entering the intersection at high speeds -- people are simply taking turns,
and the all-red period just wastes the intersection.

In PA, the lights are set on such a short cycle that if people actually
respected the yellows and the all-reds, the intersections would be empty
more than half the time.  Of course, nobody obeys the lights.  What does
PA do?  They have one of the richest communities in the country, Radnor
Township, apply for federal aid to fight red-light runners.... *sigh*.
(fortunately the money seems to be going for donuts instead)
Guys: hire some traffic engineers.

Fell free to add your own response as long as it is Constructive! It can be anonymous if you want.

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