Cities Turning to Bicycles

In article , Wayne Pein wrote:

decreasing radius turns

Such a turn could be designed explicitly for the purpose of slowing
traffic. In that case, a sign can warn of it.

If a curve is desired to slow traffic, then take the tightest radius
value and use that for a constant radius turn. It will slow traffic just
as good if not better and not have the drawbacks.

Mark Jones wrote:

"Frank Krygowski" wrote in message
...

I'm not interested in excuses about how difficult decreasing radii can be..


This is bad design. For a PE to say what you just said is ridiculous.
To resort to a decreasing radius means that the overall design is flawed.

You should be able to go through a curve without needing to slow
down the whole time. This is how you end up with trucks on their
side with their cargo spilled all over the place.

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?


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

"Alan Baker" wrote in message
...
Again, you're lying.
No need to ever hear from you again.

PLONK

Frank Krygowski wrote:

Mark Jones wrote:

"Frank Krygowski" wrote in message
...

I'm not interested in excuses about how difficult decreasing radii
can be..



This is bad design. For a PE to say what you just said is ridiculous.
To resort to a decreasing radius means that the overall design is flawed.

You should be able to go through a curve without needing to slow
down the whole time. This is how you end up with trucks on their
side with their cargo spilled all over the place.


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?


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.

This isn't that difficult a concept to grasp; I don't know why you're
having such trouble with it.

nate

--
replace "fly" with "com" to reply.
http://home.comcast.net/~njnagel

"Nate Nagel" wrote in message
...
So Frank is an engineer? I thought someone mentioned that he was a
professor? I did a quick search on his name but all I came up with were
a couple bicycling columns that seemed oddly reasonable, given his posts
here.

According to the what I could find out, he is a Professor with a
Professional Engineer(P.E.) certification. I sure looks like he
teaches in the Mechanical Engineering Technology program.

Kind of interesting what he teaches, considering that I have
a B.S. in Electronics Engineering Technology and built a
large scale automated test system that would be related
to his interests as listed on the following page.

http://www.eng.ysu.edu/tech/MET.htm

Scroll to the bottom of the page.

"Wayne Pein" wrote in message
. com...


I really find it hard to understand how he could justify a decreasing
radius turn as being a reasonable thing to build. Just because a
roading program can spit out the stakeout points for a particular
piece of roadway, that doesn't mean that it is a good idea to build it.



Such a turn could be designed explicitly for the purpose of slowing
traffic. In that case, a sign can warn of it.

The only one that I ever remember encountering did not have
any warnings posted and the posted speed was O.K. for the
entry, but not for the rest of the curve. I saw what was happening
right away and got on the brakes or it would have gotten real
interesting.

I do not like decreasing radius curves as they can be very dangerous.

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!


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

Frank Krygowski wrote:

Mark Jones wrote:


I really find it hard to understand how he could justify a decreasing
radius turn as being a reasonable thing to build. Just because a
roading program can spit out the stakeout points for a particular
piece of roadway, that doesn't mean that it is a good idea to build it.


I can tell you're finding it hard to understand! Look, let's think
about this:

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.


Any curve where the next straightaway is not visible from the entrance
to the curve, i.e. "blind" curve, yes.

If there is ANY deviation from a perfectly circular arc, there MUST be
either a decreasing radius or an increasing radius. And if the radius
increases for drivers heading west, it MUST decrease for drivers heading
east on the two-lane road.

And when this occurs, it *must* be visible to a driver entering the curve.


Obviously, this happens all the time. It's normal. And drivers handle
it in a normal fashion. If a driver has an inability to negotiate such
a curve, he's simply not competent.

ASSuming that the curve is completely visible from its entrance, yes,
this is a correct statement.


If a driver can handle it on a two lane, but not on a freeway, it can
only be because he has unrealistic expectations. I know of no design
manual that forbids these things.

If anyone _does_ know of such a manual, let's have a quote or two.


I suspect that this is probably hidden in the AASHTO Green Book, but it
is not on the web; if you want to read it you'll have to purchase a copy
from them.

nate


--
replace "fly" with "com" to reply.
http://home.comcast.net/~njnagel

In article , Frank Krygowski wrote:
Mark Jones wrote:

"Frank Krygowski" wrote in message
...

I'm not interested in excuses about how difficult decreasing radii can be..


This is bad design. For a PE to say what you just said is ridiculous.
To resort to a decreasing radius means that the overall design is flawed.

You should be able to go through a curve without needing to slow
down the whole time. This is how you end up with trucks on their
side with their cargo spilled all over the place.

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?

Right for the insulting comments. Typical Frank.

Mark Jones wrote:


I really find it hard to understand how he could justify a decreasing
radius turn as being a reasonable thing to build. Just because a
roading program can spit out the stakeout points for a particular
piece of roadway, that doesn't mean that it is a good idea to build it.

I can tell you're finding it hard to understand! Look, let's think
about this:

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.

If there is ANY deviation from a perfectly circular arc, there MUST be
either a decreasing radius or an increasing radius. And if the radius
increases for drivers heading west, it MUST decrease for drivers heading
east on the two-lane road.

Obviously, this happens all the time. It's normal. And drivers handle
it in a normal fashion. If a driver has an inability to negotiate such
a curve, he's simply not competent.

If a driver can handle it on a two lane, but not on a freeway, it can
only be because he has unrealistic expectations. I know of no design
manual that forbids these things.

If anyone _does_ know of such a manual, let's have a quote or two.


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