HomeMy WebLinkAboutCOM 0018.012 2002-2004 '~ra~c Eng~ne~~inc~~ - A+lg~ths aid Re~~~~es -
BENJAMIN E. BURRITT, P.E. viewpoints that are contrary to its windshields, glare, and adverse light-
Aasodate 4lce Prasiderrt, personal opinions and emotions. ing conditions.
Daniel, Mann, Johnson, b Mendenhall, My[h Number 2: Traffic control MeanwhIle, pedestrians' views of
Phoenix, Arizona devices (signs, signals, and markings) the same crosswallc are quite impres-
provide an effective solution to almost sive and they .ve prone to assume
~RAFFIC engineers and the public any traffc problem. that, since they can see the crosswalk
often carry severe handicaps Reality: There is widespread pub- so well, certainly motorists can see it
when dealing with each other be- Gc umvillingness to accept abundant just as clearly. This resulting overcon-
` cause they supply do not talk the same evidence of limited effectiveness of fidence is seen as another factor in the
1f language, they do not understand the various devices in solving basic desrgn disproporttonatexhare oCaccidents m
I nature of each other's problems, or or construction defimencies. The marked crosswalks.
both. This is understandable when political need to "do something that Does this mean marked crosswalks
a you realize that engineers approach might help, doesn't cost much, and should not be installed? Not necessar-
~ ~ traffc problems on the basis of data can'[ hurt" is overpowering and ily. The marked crosswalk is a useful
m'...~ V analysis, applying engineering prm- further encourages the public de- device For channelizing pedestrians
w t ciples, developing alternative so- mand. The fallacy lies in thinking that and helping pedestrians find their
w i it e~ futions, and selecting the best course a safer condition prevails when actu- way across complex and confusing m-
rt7 Q ofaction-whereas the citizeni:;usu- ally this may not be the case. tersections. The decision to install or
ally interested in getting something Let's take a look at a few of the not install a marked crosswalk should
i ~ done quickly to solve what he per- common traffic controk in view of the not be taken lightly. Rational war-
~ ceives to be an obvious problem. myths and the realities. rants have been adopted by many
P One oC the greatest obstacles apro- pBd25tr1aO GOSSWalkS governmental jurisdictions for their
Cessional traffic engineer (aces in ap- installation.
plying sound principles of traffic con- How safe are they? How secure are It is important that the general pub-
tro is that everyone who has a you in a crosswalk? Marked lie recognize what marked crosswalks
~ dri Br's license is convinced that they crosswalks are widely classified as can and cannot do. It is also important
traffic experts. Consequently, [he "safety devices" and most jurisdic- [hat public officials not install them,
a fie engineer is often given not only lions give the pedestrian the right- unless the anticipated benefit ; nut-
diagnosis of a traffic problem, but of-way when within them. weigh the risks.
emedy as well. For example, Interestingly, however, [here is Traffic Signals
cone calls and says, "I almost got strong evidence that these very Facts
t urning IeFt a[ Buckeye Road and prompt many pedestrians to Ceel Are traffic signals the answer to in-
1 Avenue -what we need there is overly secure when using a marked tersection traffic problems? Let's look
o I Ct turn arrow -how long will it crosswalk - to the degree that they at the advantages and disadvantages.
Z c ~q. tae to punt in7"In asense this would aggressively place themselves in a Signals offer maximum control at
~ Z ~ 6~ike calling your doctor and saying, hazardous position with respect to intersections -they relay messages
B y O: "Doc. I've go[ a pain in my stomach - vehicles in the mistaken belieFthat the of both what to do and what not to do.
~n ~ w~:zt 1 need is my appendix removed motorist can and wdl stop m all cases, The primary function of any traffic
- huw soon can you do the opera- even when it may be impossible to do srgnal is to assign right-of-way to con-
tron?" so. It is pat unusual, also, For this type tlicting movements of traffic at an tn-
At this pant let me hasten to say of aggressive pedestrian behavior to tersection, and it does this by permit-
that most traffic engineers encourage cause rear-end collisions. ling conflicting streams of traffic to
information, suggestions, and input By contrast, a pedestrian using an share the same intersection by means
from the public. This is one of the unmarked crosswalk generally feels of time separation.
ways [ha[they become aware oFexist- less secure, less certain that the IIy alternately assigning right-oF-
mg or potential traffic operational motorist will stop - and exercises way [o various traffic movements,
problems. Engineers must be ren~p- more caution in waiting for safe gaps signals provide for the orderly move-
tive to input From the public and at- in traffic before crossing. The end re- meat of conflicting flows. They may
tempt to overcome the built-in hand- stilt is Fewer accidents at unmarked interrupt extremely heary (low; to
icaps by trying to communicate in ? cro-swalks. permit the crossing of minor
common understandable language. One of the commonly accepted movements that could not otherwise
What 1 would like to do now is to functions oC the marked crosswalk is move safety through the intersection.
review a couple of the myths and [hat it serves as a warnuig device to bVhen properly tuned, [he traffic
realities pe rtaimng to traffic engineer- the motorists. Yet, studies show that signal increases the tra F(ic handling
ing and traffic controls. themotonsts'viewsofacrosswalkare capacity of anmtersecuon, and when
Myth Number 1: The pubGe knows greatly reduced when they are at the installed under conditions that jus hCy
and Bares about traffic engineering safe stopping sight distance -where ds use, it is a valuable deuce For im-
prtnciples, obj ec[ivcs, analyses, nl- they should be able to perceive and proving the safety and efficiency of
Lernau vas, or methods. react to a pedestrian in a crosswalk - both pedestrian and vehicular traffic
Reality: The familiar expression due [o the effects of foreshortening In particular, signals may reduce c cr-
"Don't confuse me with facts, my and distance diminishment. Their tam types of acceienls, most notably
mind is made up'" unforhmately has vieuv of the crosswalk is further aF the angle tbroadsidel collison.
widespread acceptance. The public is leered by road aliKnment, ir- Whde many people realize that tr-af
handicapped bs~ a short attennun rc r;ulanties m the pavement, and he sir;nals can reduce the number of
span :end an iv~~rann to facts. login. sir other variables like weather, dirty ankle collisons at nn nnerecuon, fe:+~