Cities Turning to Bicycles

Frank Krygowski wrote:

Nate Nagel wrote:


Blind curves should *never* be decreasing radius. Never. If a road
has traffic in two directions, a blind curve should be, by necessity,
constant radius.


:-) I thought you had driven in West Virginia. And Western Pennsylvania.

So every road that has to curve around an Appalachian hill should have
the hillside sculpted into a perfect circular arc?


There's a huge difference between a western PA goat track and an
Interstate highway. A road cut into a hillside you expect to be
surprised, and allow a little extra cushion in your speed. Especially
when said Interstate highway has a curve in it that looks for all the
world like a standard cloverleaf kind of thing until you're already
committed to it.

I'll post this again, since you clearly didn't look at it the first time:

http://www.gribblenation.com/hfotw/exit_50.html

Notice how there appears to be maybe a 55 MPH typical cloverleaf as you
enter the turn, but once you get maybe 20 degrees in you suddenly
discover that it's actually a sharp hairpin and what you thought was the
actual curve was really nothing much at all. Again, poor highway design.

But the point is, **** happens. Sometimes highways get built with less
than optimal design features, and we have to deal with them. This one
is particularly bad, as it's deceptive. So there are warning signs to
alert drivers to the special hazards of the situation. The question
that has remained unanswered throughout this long, tedious thread is,
"how do you communicate to motorists the concept of 'yes, I know every
exit ramp on the East Coast is signed at 25 MPH which is generally 20
MPH pessimistic, but even though this sign looks exactly like all those
other signs and you aren't even exiting the freeway, we really, really
mean it this time, so slow down.'"

To extend it to the discussion of your neighborhood, the analogy is "I
realize that you do most of your driving on the freeway, where the speed
limit signs are generally 20 MPH or more pessimistic, but even though
this 25 MPH sign looks just like those freeway speed limit signs, we
really, really mean 25 MPH, so slow down."

Heck, perhaps you should just have *that* printed on a sign, to go on
the same post as the speed limit sign. At the very least, I'd get a
chuckle out of any municipality that had the balls to post something so
honest.

nate

--
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"Frank Krygowski" wrote in message
...
Nate Nagel wrote:


Blind curves should *never* be decreasing radius. Never. If a road has
traffic in two directions, a blind curve should be, by necessity,
constant radius.

:-) I thought you had driven in West Virginia. And Western Pennsylvania.

So every road that has to curve around an Appalachian hill should have
the hillside sculpted into a perfect circular arc?
This has devolved from the original discussion concerning freeway
exit ramps. That is where I do not consider decreasing radius
to be a good idea.

In the mountains, you just have to slow down and understand that
the curves can have varying radii and can even switch directions
part way through them.

These are two very different design situations and drivers in the
mountains should expect the road to be very complex. You get
all kinds of compound curves and elevation changes going
both up and down over relatively short distances. If you drive
fast in a unfamiliar place in the mountains, it may be the last
thing you ever do.

Arif Khokar wrote:

Nate Nagel wrote:

[I-79 curve]

To return to the original point of this whole example - it is clear
that there are times and places where greatly reduced speeds may be
necessary for safety reasons.


IIRC, that particular curve is accompanied by a series of reduced speed
ahead and reduced speed limits rather than advisory speeds. I believe
that within a mile it drops from 65 to 55, then 45, then 35, and finally
25 mph. If there were only advisory signs, there would be a lot more
crashes because a decreasing radius curve that can be negotiated at 35
mph max is the last thing one expects on an interstate (and exemplifies
the inherent problem with chronic misuse of advisory signs on most roads).

You may be right, it's been a couple years since I've been up that way,
and I was unable to find a good picture on the web of the actual
signage. However, you just described to a tee the signage on I-70 as
you approach US-30 in Breezewood, which is a complete non-event - yeah,
there's a tee intersection with a traffic light, but you can see it from
a mile away. Same thing with the rumble strips and reduced speed signs
two miles before a toll plaza. Obviously PA highway engineers never
heard of Chicken Little.

Speaking of which, whose brilliant idea was it to plunk down a toll
plaza right in the middle of the PA Turnpike? Freaked me right out the
first time I saw it. One thing the 'pike had going for it over other
toll roads was that you paid when you entered the state or got onto the
'pike, and then didn't have to stop again until you got off or left the
state on the other side.

nate

--
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"Frank Krygowski" wrote in message
...
Say you're laying out a two-lane road. Are you prepared to say every
curve MUST be a constant radius - that is, a circular arc? Of course
not. That's impractical, given difficulties with contours, rivers,
right-of-way access, etc.
We have wandered away from what we were originally talking about
and I wasn't clear enough in what I wrote. The only place where
I feel that varying radius curves shouldn't be used is on the exit ramps
where a clover leaf design is used. I have seen overturned trucks
on these and learned for myself one time just how dangerous
they can be if you enter the ramp even a little too fast.

I could picture what I thought we were talking about, but I wasn't
aware that the scope of this had broadened to cover the open
highway.

In the hills, varying radius curves are used all the time. I have driven
in the mountains, and you need to pay attention to the posted limits
if you value your life. This is particularly true if you are unfamiliar
with the area.

Alan Baker wrote:

I've driven my brother's Nissan Pathfinder (even before it had its
shocks replaced) and it can easily -- easily -- more than double the
advisory speeds on most ramps.

Advisory speeds are based on the comfort level of a driver driving a
1939 Ford Vehicle. The lateral force would be enough to have a "ball on
a string" deviate 10 degrees from the vertical position. Most drivers
take curves such that the deviation would be between 12 and 14 degrees,
IIRC.

Mark Jones wrote:
"Frank Krygowski" wrote in message
...

Are you saying you couldn't handle a decreasing radius curve? Do _you_,
personally, need to have only _increasing_ radius curves to be able to
successfully stay on the road?

How about on a two lane road? Do you want to see only increasing curve
radii when you're heading, say, east?

And Mark - what sort of engineering tricks do you want used when you
turn around and drive west?


They are called constant radius curves. Much safer than decreasing
radius curves.


IOW, you seriously think all curves must be constant radius. Astonishing!

I might expect this idea to come from a novice driver just learning to
steer - and unaware of the complexities of real life engineering. But
for a licensed driver to say this is amazing.

I suggest you get a 1:24000 USGS map of any hilly area you plan to drive
through. Examine it in detail before you leave. You'll find _many_
curves you'll want to avoid.

--
Frank Krygowski [To reply, remove rodent and vegetable dot com.
Substitute cc dot ysu dot
edu]

Brent P wrote:

In article , Frank Krygowski wrote:

Brent P wrote:


I would suggest Frank ride his bicycle through a decreasing radius turn
that wasn't visable until he was in it such that it forced him to brake
hard. This would probably be the best lesson as to why this sort of
design should be avoided. Braking while turning is as ill-advised on a
bicycle as it is driving. Probably more so.

:-)

Almost every time I make a turn on the bike, it's done with a decreasing
radius, and with braking while in the turn! This is normal for a bicycle!


Sheesh. Newbies!


Not braking by coasting frank. braking with the brakes. Coasting is
normal on the road, not squeezing the hand brakes.

Yes, braking with the brakes, Brent. While in a curve. Every day.
It's quite normal.


--
Frank Krygowski [To reply, remove rodent and vegetable dot com.
Substitute cc dot ysu dot
edu]

Nate Nagel wrote:

Frank Krygowski wrote:

Nate Nagel wrote:


Blind curves should *never* be decreasing radius. Never. If a road
has traffic in two directions, a blind curve should be, by necessity,
constant radius.



:-) I thought you had driven in West Virginia. And Western
Pennsylvania.

So every road that has to curve around an Appalachian hill should have
the hillside sculpted into a perfect circular arc?


There's a huge difference between a western PA goat track and an
Interstate highway. A road cut into a hillside you expect to be
surprised, and allow a little extra cushion in your speed.

Seems to me you should _always_ allow a reasonable cushion in your
speed. If you ever find yourself driving at ten tenths on a public
road, you've made a mistake.

Now, mistakes happen. But it's a bit immature to admit your mistake,
describe it in great detail, then try to pass it off as impossible to
avoid. And that's pretty ineffective, too, when others can point out
that they did _not_ make that mistake.

And if you meant the mistake was merely difficult (not impossible) to
avoid - then those who have avoided it have demonstrated greater
competence than you did, haven't they?

--
Frank Krygowski [To reply, remove rodent and vegetable dot com.
Substitute cc dot ysu dot
edu]

Mark Jones wrote:


This has devolved from the original discussion concerning freeway
exit ramps.

It's now far removed from the issue which concerns me - which is
controlling irresponsible drivers in non-freeway situations. I should
bow out.


--
Frank Krygowski [To reply, remove rodent and vegetable dot com.
Substitute cc dot ysu dot
edu]

In article , Frank Krygowski wrote:
Brent P wrote:

In article , Frank Krygowski wrote:

Brent P wrote:


I would suggest Frank ride his bicycle through a decreasing radius turn
that wasn't visable until he was in it such that it forced him to brake
hard. This would probably be the best lesson as to why this sort of
design should be avoided. Braking while turning is as ill-advised on a
bicycle as it is driving. Probably more so.

:-)

Almost every time I make a turn on the bike, it's done with a decreasing
radius, and with braking while in the turn! This is normal for a bicycle!


Sheesh. Newbies!


Not braking by coasting frank. braking with the brakes. Coasting is
normal on the road, not squeezing the hand brakes.

Yes, braking with the brakes, Brent. While in a curve. Every day.
It's quite normal.

Not surprising given your other foolishness. It also shows that you
likely putter along at sidewalk speeds. At the road speeds I ride
braking in a turn on a bicycle begins to overtax the avialable traction.

A bicycle like any other vehicle has a finite amount of traction. It can
be used for braking, accelerating, or turning and any combination there
of. This is why it is proper form to brake before entering the turn. I
brake to the speed I can take the turn at, remain at that speed or coast
into the turn and accelerate out.