Cities Turning to Bicycles

fbloogyudsr wrote:


Yes, he's a prof at Youngstown, has a BS & MS in Engineering (looks like
the general engineering type of degree), along with a PE license (in
Penn, not OH).

Nope. Ohio too.


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

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).

"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.

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.

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?



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

"Frank Krygowski" wrote in message
...
How about on a two lane road? Do you want to see only increasing curve
radii when you're heading, say, east?

Might have to ask my brother what kind of problems he has seen
with these. He is a policeman and has had to work a lot of vehicle
accident scenes.

"Frank Krygowski" wrote
fbloogyudsr wrote:
Yes, he's a prof at Youngstown, has a BS & MS in Engineering (looks like
the general engineering type of degree), along with a PE license (in
Penn, not OH).

Nope. Ohio too.

Then update your "home page" on the Y. U. site.

Floyd

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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