[Talk-ca] Routing errors, turn restrictions and median crossovers

James Ewen ve6srv at gmail.com
Mon Mar 7 06:06:57 GMT 2011


On Sun, Mar 6, 2011 at 5:20 AM, Stewart C. Russell <scruss at gmail.com> wrote:

> If it's any consolation, Garmin's maps will suggest u-turns in the
> middle of highways too. Every time I want to go to Point Edward, the
> Garmin tells me to pull a U-ey in the middle of the 402.

That's not a u-turn... it's a sharp left!

I think every routing engine figures that a u-turn can only take place
on a non-divided highway. As soon as you have a dual carriageway, then
"rippin' a 180" is fair game. Even so, where that dual carriage way
ends and forms a Y with a single carriageway, my GPS navigator thinks
that's a good place to spin around.

Looking at it from a computer coding point of view, how do you
determine when that little bit of road between the opposing lanes is
no longer a cut in the median, but a street on it's own?

To be fair, most humans these days can't figure out what a cut in the
median is... There are so many idiots out there that think it is legal
to pull across a set of lanes, and stop in the median waiting for a
break in the traffic traveling in the opposite direction. Or even
better boneheads that are signalling for a left hand turn while you
are doing the same facing them that try to go around you to their
right  in the middle of the intersection before completing the left
hand turn. Both of these maneuvers are not only dangerous, but
completely illegal.

I've taken to sitting at dual carriageway intersections waiting to
make a left turn until there are no more oncoming vehicles facing me
with left turn signals on. If I try to drive properly there's a good
chance for a collision or at the very least a bunch of finger action
from the bozo that is breaking the law.

Even the "experts" who design the roadways aren't in the clear... we
have a dual carriageway in Edmonton with a fairly wide median. The
traffic planning experts put an extra set of lights in the middle of
the intersection as well. When making a left hand turn, you have to
stop for the set of lights to cross what used to be the oncoming
lanes. There's room for about 2 passenger cars to make the turn on
each change of lights. A large semi ends up blocking the intersection
because the trailer hasn't cleared the roadway by the time the
steering axle hits the stop line. Put two B-trains opposing each other
and that intersection is done...

I can't recall where that intersection was... I haven't been by it for
years. Had a quick look at the map, but it's not coming to me. Maybe
it has been removed and corrected now.

The traffic planners have resorted to putting in long left hand turn
lanes which put the opposing drivers to the left of the oncoming
vehicles in an effort to keep people from attempting to interlock the
vehicles while making left turns...

http://www.openstreetmap.org/?lat=53.46537&lon=-113.466058&zoom=18&layers=M

The days of the Uniform Traffic Act are long gone.

James
VE6SRV



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