HomeMy WebLinkAbout03-05-18 Public Comment - R. Zimmer (on behalf of the PTS Committee) - I-90 Speed LimitFrom: Robin Crough
To: Agenda
Subject: FW: City Advisory Board Recommends Lowering I-90 Speed Limit
Date: Monday, March 05, 2018 8:15:47 AM
From: Ralph Zimmer [mailto:RalphZimmer@mcn.net]
Sent: Monday, March 5, 2018 7:23 AM
To: Cyndy Andrus <CAndrus@BOZEMAN.NET>; Chris Mehl <CMehl@BOZEMAN.NET>; Jeff Krauss
<Jkrauss@BOZEMAN.NET>; I-Ho Pomeroy <IPomeroy@BOZEMAN.NET>; Terry Cunningham
<TCunningham@BOZEMAN.NET>
Cc: Andrea Surratt <ASurratt@BOZEMAN.NET>; Craig Woolard <CWoolard@BOZEMAN.NET>;
Richard Hixson <rhixson@BOZEMAN.NET>; Steve Crawford <SCrawford@BOZEMAN.NET>; Richard
McLane <RMcLane@BOZEMAN.NET>; Josh Waldo <JWaldo@BOZEMAN.NET>; Robin Crough
<RCrough@BOZEMAN.NET>; Danielle Scharf <DScharf@sandersonstewart.com>; Mandee Arnold
<MandeeMT@gmail.com>
Subject: City Advisory Board Recommends Lowering I-90 Speed Limit
Monday, March 5, 2018
Mayor Andrus and Bozeman City Commissioners,
I am writing on behalf of the Bozeman (Area) Pedestrian and Traffic Safety Committee,
the City's Advisory Board on ground transportation matters and particularly on traffic safety
matters. At its meeting this evening, the City Commission will be considering one of those
matters, namely the proposal to request the State to lower the I'-90 speed limit to 65 MPH in
the vicinity of Bozeman
PTS voted on both December 13 and February 14 to recommend that the I-90 speed limit
in the Belgrade/Bozeman area be lowered to 65 MPH. Both votes were unanimous. It is a
safety matter.
There Are SEVERAL, NOT "Just" One, Safety Concerns
One safety concern has received a fair amount of attention in the media, namely the
safety of emergency personnel responding to incidents on I-90. I have seen the statistics and
they are eye-opening. The three fire departments (Central Valley, Bozeman, and Fort Ellis)
are called to incidents on I-90 about three hundred times a year! These are crashes, vehicle
fires, hazardous material spills, grass fires, etc. Law enforcement personnel are there
additional times making traffic stops,etc Given the high volumes and the existing 75 MPH
speed limit, , these incidents present a real hazard to those public safety personnel and their
equipment. It truly is a work place safety issue.
However, there are other safety issues not involving such incidents and these other issues
are also very important. One of these is "stacking". This occurs when the exit ramps are so
backed up that vehicles wishing to exit must slow significantly and sometimes even stop
before leaving the through lanes on the Interstate. This results in a lot of lane changes and
weaving operations, all of which are hazardous at the high speeds and high volumes on the
Interstate. There is risk of rear-end and sideswipe crashes. The relative high speeds in the
through lines leaves less time for drivers to find the gaps needed to safely change lanes.
High volumes and high speeds are a deadly combination High volumes result in fewer
and shorter gaps for changing lanes in order to pass, to get to an exit ramp, or to avoid
"stacking". The higher the speed, the riskier is the diversion of the motorist's attention as
they look for gaps in the adjacent lane and the more disastrous are any resulting crashes.
Because of less than desirable horizontal and vertical geometry, the westbound entrance
ramp onto I-90 at the East Main interchange is undesirably hazardous. Safety would be
increased if westbound through traffic at that interchange were traveling at a lower speed.
There are other safety benefits that would occur if the speed limit were dropped to 65
MPH and that lower limit extended further east and west than the city's jurisdictional area
All of the safety concerns mentioned above are exasperated by the combination of high
volumes and high speeds. The Montana Department of Transportation's own data shows that
the volumes on I-90 in Bozeman rival or perhaps even surpass those of Billings, and those
volumes far surpass those in Butte, Great Falls, and Missoula Those volumes in Bozeman are
growing rapidly and there is not much that can be done to reduce them The speed limit, on the
other hand, is something that within reason can be controlled 65 MPH would be much better
than 75 MPH,. Billings, Butte, Great Falls, and Missoula all presently have 65 MPH speed
limits Bozeman doesn't.
Apples & Oranges
There is a State law that mandates that motorists approaching an emergency incident on a
highway must slow down by 20 MPH and, if possible, move over into the adjacent lane.
Some people have said that the 65 MPH speed limit is not needed because that 20 MPH
reduction requirement means vehicles will be passing those emergency incidents at only 55
MPH and 55 is even less than 65. That is an invalid comparison. It is comparing apples to
oranges.
It would be valid to compare the posted speeds (75 ms 65). It also would be valid to
compare the allowable speed when passing an emergency incident (55 vs 45). The conclusion
is inescapable. Lower speeds would result from lowering the posted speed limit from 75 down
to 65 MPH. Safety would be increased by lowering the existing posted speed limit.
A Traffic Engineer Responds to Commissioner Krauss
If the speed limit for passenger vehicles were lowered to 65 MPH, the assumption is the
speed limit for trucks would also be 65 MPH. At the October Transportation Coordinating
Committee (TCC) meeting, Commissioner Krauss said he would only be willing to support
reducing the posted speed to 65 MPH if the speed limit for trucks were reduced to something
under 65 MPH. I suspect that is still his position and I would like to give a traffic engineer's
response to that position.
Everything else being equal, traffic engineers like to have both uniformity in driving
speeds and consistency in speed limits. Both contribute to safety.
If every vehicle driver chose to drive at exactly the same speed, there would be no
passing and no lane changes (except as needed on entering or leaving the highway).
Differential speed limits are passenger vehicles and trucks are defensible if traffic volumes are
relatively low and thus there are numerous and lengthy gaps for passing. As mentioned above,
we have high, not low, volumes on the Interstate in Bozeman.
Consistency and predictability in speed limits is desirable. Passenger vehicle drivers in
Montana know that the Interstate speed limit in Billings, Butte, Great Falls, and Missoula is 65
MPH and thus they would not be surprised to find that the speed limit in Bozeman is also 65
MPH. Similarly, truck drivers in Montana know that their speed limit in those other four
Montana cities is 65 MPH and thus they would expect it to be 65 in Bozeman Plus the speed
limit for trucks would remain 65 MPH both in those Montana cities and outside those
Montana cities thus giving truckers consistency and predictability.
Also, if a passenger vehicle wanted to exit the interstate at some particular interchange
and if the speed limit for trucks were lower than for passenger vehicles the trucks would tend
to create a moving fence making it more difficult and more hazardous for them to get into the
right hand lane to reach the exit ramp.
Why JUST a Temporary Speed Reduction?
It appears the quickest and easiest way to get the speed limit lowered to 65 MPH would
be by getting the State Transportation Commission to exercise its authority to set a "temporary
reduced speed limit" of 65 MPH , so that is the route we are encouraging. The 65 MPH speed
limit would be posted and there would be no indication to the motorist that it is a "temporary"
speed limit
The speed limit would remain "temporary" until at some future date the State
Transportation Commission either made it permanent or revoked it. That decision would be
based on an "engineering and traffic study" to be done by the Montana Department of
Transportation
It conceivably might take years before that decision was made. The reduced speed limit
on the Interstate in Butte took eight years to be changed from "temporary" to "permanent".
Personally, I would be glad if that determination in Bozeman were postponed until after the
2020 census results were known. Those results plus traffic volumes that undoubtedly will
have grown even larger would increase the probability the "temporary" limit would be made
"permanent".
Concluding Comments
Three of the voting members of our committee are transportation engineers/traffic and I
again emphasize that the committee voted unanimously to recommend the 65 MPH speed
limit. My personal opinion is the work place safety issue for our emergency responders by
itself would justify the proposal Also, in my personal opinion,, other safety concerns would
by themselves justify the proposal.
Lowering the speed limit will not be a panacea. It will not make I-90 safe. However, it
will make it safer. There still will be crashes although perhaps not quite as many (at least
relative to the traffic volumes) There still will be injuries and unfortunately perhaps even
fatalities. However, there should be a statistically significant decrease in incapacitating
injuries and fatalities (at least relative to traffic volumes).
In short, we should not have over-expectations but we will achieve positive results and
that is exceedingly important. Please request the State to set the I-90 speed limit in the
Bozeman area to 65 MPH for both passenger vehicles and trucks.
Ralph W. Zimmer, Ph.D., P.E. (inactive)
Chairperson, Bozeman (Area) Pedestrian and Traffic Safety Committee
cc: Andrea Surratt
Craig Woolard
Rick Hixson
Steve Crawford
Rich McLane
Josh Waldo
Robin Crough
Danielle Scharf (PTS Vice Chairperson)
Mandee Arnold (PTS Secretary)
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