Sent: Thursday, January 10, 2002 3:57 PM
Subject: TRB Items. Rumble Strips etc.
While recent research and
reports issued by PennDOT, CalTrans, ColoDOT, and most recently FHWA, contain
much useful info, Shoulder Rumble Strip (SRS) Issues Are Not Yet Settled, and
still need close attention by ASCE HPT Com as well as all pertinent
parties.
1. Milling machines
can install over 10 miles of divots in one day, can do a lot of damage in a
hurry that is not easily fixed. Anyone who has ever been involved in
trying to obtain any mileage of Bike Route anywhere, perhaps requiring years of
planning, hassles, meetings, tradeoffs, consensus building, bond issues,
possibly hundreds of thousands or millions of dollars, etc, or anyone who has
ever utilized a paved shoulder as a pleasant, relatively safe, hassle-free bike
route from one place to another, will know the sinking feeling that comes with
seeing an arbitrary decision with little or no oversight turning loose a machine
that destroys 10 miles of bikeable shoulder in just one day at a cost of 10
cents a foot. Sometimes difficult for DOTs to resist. It's
important that SRS not be indiscriminately placed everywhere, which is
becoming more common. A big temptation. Need better criteria for
warranting SRS installations on non-freeway roads.
2. Design of all SRS
is essentially based on Large Truck response, resulting in harsh
SRS everywhere. Caltrans Study found
only 4 fatal sleep related run-off-road (ROR) large truck crashes on Calif roads
over 3 year period, and noted RS placement should focus on passenger vehicle ROR
and needs of bicyclists. While Caltrans Study may not be typical
everywhere, there is still a need to set accident criteria requirements before
installing harsh RS (or any RS at all) on non-freeway type roads with narrower
shoulders. Narrow shoulders warrant the
less harsh SR because of closer contact with bikes.
3. Item 9b(2) of
12/20/01 FHWA Tech Advisory states that gaps in the strip pattern may be more
effective in allowing safe crossings than modest reductions in the depth of each
milled strip. Possibly a damaging statement which may be interpreted as
giving OK to any degree of harshness or any RS as long as RS has
intermittent gaps. Gaps are definitely a step in the right direction
and should be encouraged but they do not eliminate need for less harsh RS.
Cyclist does not always have choice of where or when to cross any RS.
Also, harsher RS require more shy distance
4. FHWA Item
9b(3) OKs RS in very narrow shoulders if min 1 ft clear remains between RS
and edge line for cyclist to ride. Also possibly a damaging statement,
which could OK taking existing 2 and 3 ft shoulders away from cyclists.
Needs judgment in use.
5. FHWA says 3/8"
deep grooves OK, while Caltrans felt groove depths of 3/8" too harsh
for cyclists. Difference probably is groove width in direction of
travel, which is not clear in FHWA. Groove widths in direction of travel
should be spelled out, as larger groove widths produced by larger grind wheels
can allow greater wheel drop. (6" wide allows 1/8" greater wheel drop
than 5", etc).
6. Field experience
shows difficulty in obtaining close depth and longitudinal width
tolerances with grind wheels, and close attention needs to be paid to contractor
ability to achieve desired grooves prior to starting work. Depth
specs that target 3/8" plus or minus 1/8" (eg ColoDOT report),
allow 1/2" depths which showed too harsh in ALL research
reports. A bike friendly SRS satisfactory to all concerned is not yet in
use. Other configurations should not be ruled out.
7. Arizona using 1/4" depths with 4"
to 5" widths in direction of travel by 5" to 8" in transverse width, placed in
or adjacent to edge stripe of narrower shoulders. Should
track effects of these and other less harsh RS re. both cyclists and
motorists.
The above doesn't cover
all the bases but is a starting point. One thing that hasn't changed
over the past 6 to 8 years. You can still ruin the whole day for cyclists
by using the RS word.
Mac
Elliott