Why We Are Stuck at High Speed, and What We Are Going to Do About It

8/2/2019 Why We Are Stuck at High Speed, and What We Are Going to Do About It

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Why Were Stuck at High Speed,and What Were Going to Do About It

Sara Wright & Scott BrickerFebruary 2012

I. Introduction

Many people are concerned about the speed of automobiles in their community. Higher speeds

create both a traffic safety hazard, and an environment in which people are uncomfortable

walking. As driving speed increases, so does the likelihood of getting into a crash, and the

likelihood of injury or death for the people involved in the crash. The risk is greater for peoplewho are walking or biking, and thus more vulnerable to injury than vehicle passengers. When a

vehicle traveling about 23 mph hits a pedestrian, the pedestrian has an 25% average risk of

severe injury and a 10% average risk of death. When the vehicle is traveling about 32 mph,

those average risks change to about 50% and 25%, and at 40 mph, they are about 75% and

50% (Tefft 2011). Speeds of 25 to 40 mph are standard in urban areas, where many people on

the roads are walking and biking. The way our roads are planned and built puts lives at risk in

our communities every day.

For more than half a century, designing and building roads that maximize travel speed has been

the central goal of transportation engineering. The first roads in the United States were built for

slow-moving traffic - people and animals moving at walking speed. As the car became a popular

way to travel, the road system was increasingly built for speed. Our modern transportation

planning paradigm was born in the 1950s, when the National Highway System was launched,

and the design standards and practices developed at that time were aimed at maximizing travel

speed. Those standards and practices continue to inform the way we plan and build roads now,

in spite of the dramatic societal changes over the intervening 60 years.

Changing speeds on your street or in your community can be a difficult undertaking. When

approaching transportation professionals and engineers, it is important to understand how they

think about speed and speed limits, as well as the technical terms and practices that contribute

to higher speeds. This paper describes the way that many transportation professionals continueto think about speed, outlines some of the challenges for changing the way we address speed in

our communities, and identifies some areas where we can begin to shift the paradigm.


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II. How Do Transportation Professionals Think AboutSpeed?

Three Types of Speed

From a traffic engineers perspective, there are three kinds of

speed:

Operating Speed - the speed at which people actuallydrive on the roadway under free-flow conditions. This isusually pegged at the 85th percentile - the speed that

85% of drivers are traveling at or under. Design Speed - the speed the road is designed to

safely accommodate. Posted Speed - the speed limit posted for the

roadway.

(The jargon of transportation engineering and planning can bedaunting - helpful glossaries by theFederal HighwayAdministrationand theFlorida Department of Transportationcan be found on their websites.)

What Influences Operating Speed?

Operating speed is what you experience on the roadway, thespeed at which people drive their vehicles each day; this istypically measured by the 85th percentile driving speed.Transportation professionals generally agree that free-flowoperating speed is a response to the design of the road (howmuch it curves, how far ahead you can see, its width, etc.) andits surrounding environment (pedestrians, street trees, parkedvehicles), rather than to the posted speed limit. The

What is the 85th

percentile rule,

anyway?

The 85th percentile

rule is a way

engineers determine a

reasonable driving

speed for a road. After

collecting data on

observed speed of

drivers on a particular

road, engineers

identify the speed

under which 85% of

drivers are travelling.

The underlyingassumption is that

most people drive at a

safe speed, except for

a few reckless outliers,

and that speed is

therefore appropriate

for the road. Under the

current engineering

and transportation

planning paradigm,

this is considered to

be a rational,

pragmatic, and safe

way to set operating

speed. Many states

use the 85th percentile

as a standard for

setting speed limits,

and set high barriers

to using any other

factors.
http://www.fhwa.dot.gov/Planning/glossary/glossary_listing.cfmhttp://www.fhwa.dot.gov/Planning/glossary/glossary_listing.cfmhttp://www.fhwa.dot.gov/Planning/glossary/glossary_listing.cfmhttp://www.fhwa.dot.gov/Planning/glossary/glossary_listing.cfmhttp://www.dot.state.fl.us/planning/glossary/glossary.pdfhttp://www.dot.state.fl.us/planning/glossary/glossary.pdfhttp://www.dot.state.fl.us/planning/glossary/glossary.pdfhttp://www.dot.state.fl.us/planning/glossary/glossary.pdfhttp://www.dot.state.fl.us/planning/glossary/glossary.pdfhttp://www.dot.state.fl.us/planning/glossary/glossary.pdfhttp://www.dot.state.fl.us/planning/glossary/glossary.pdfhttp://www.dot.state.fl.us/planning/glossary/glossary.pdfhttp://www.dot.state.fl.us/planning/glossary/glossary.pdfhttp://www.dot.state.fl.us/planning/glossary/glossary.pdfhttp://www.fhwa.dot.gov/Planning/glossary/glossary_listing.cfmhttp://www.fhwa.dot.gov/Planning/glossary/glossary_listing.cfmhttp://www.fhwa.dot.gov/Planning/glossary/glossary_listing.cfmhttp://www.fhwa.dot.gov/Planning/glossary/glossary_listing.cfmhttp://www.fhwa.dot.gov/Planning/glossary/glossary_listing.cfm


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engineering consensus about operating speed is that people drive as fast as they think is safe,based on road and environmental conditions, and thats often faster than the posted speed(Fitzpatrick et al. 2003). Therefore thedesign speedeffectively dictates theoperating speed,much more so thanposted speeddoes. Education and enforcement efforts can also make adifference in operating speed, but they must be sustained (e.g., installation of speed cameras).

How Are Design Speeds Set?

When a road is to be built or rebuilt, the first step is to decide on the classification of theroadway. Roads are classified generally as arterials (fastest travel, least access to destinations),collectors, and local streets (slowest, most access to destinations), with a variety of sub-classifications. The classification of the road then determines the range of design speed options,which are typically selected from a state manual or from the American Association of StateHighway and Transportation Officials manual, A Policy on Geometric Design of Highways andStreets, which is referred to as TheGreen Book. (Fitzpatrick et al 2003).

Unfortunately for people walking, roadway engineers and designers often choose the highestpossible design speed from that range, based on the belief that a higher-speed roadway is also

a higher-quality roadway (PPS 2008). This is backed by the fact that federal and state fundingallocation often prioritizes construction and maintenance of higher order roadways, creatingadditional incentive to choose the highest possible roadway classification (Urgo et al 2010).The higher road classifications also have higher design speed ranges.

How Are Posted Speed Limits Set and Enforced?

Speed limits are set based on the ranges assigned by the state to each roadway classification.While states have a wide variety of legal guidelines about how speed limits are assigned, theygenerally hew to recommendations for specific types of streets, often based on the Green Book.Engineers usually have some flexibility in the speed limits they choose from the menu ofoptions.

Many transportation agencies subscribe to the ideaarticulated by the Oregon DOT that most people arereasonable and laws exist to control the few who areunreasonable or inconsiderate (ODOT website) Speedlimits, therefore, are intended to guide the fewunreasonable people and to set a threshold that can beenforced without stretching limited police budgets too far ormaking too many people angry.

III. How Do We Get to Truly Reasonable Speeds?

We find ourselves stuck in a transportation planning

paradigm that was developed in an environment completelydifferent than where we are now. We continue to buildroads that encourage high driving speeds, at the expense ofour health, our safety, and our government budgets. Thereare many factors that keep us stuck. America Walksidentifies the following list as some of the key challenges toreasonable speeds.
http://www.oregon.gov/ODOT/HWY/TRAFFIC-ROADWAY/speed_zone_program.shtmlhttp://www.oregon.gov/ODOT/HWY/TRAFFIC-ROADWAY/speed_zone_program.shtmlhttp://www.oregon.gov/ODOT/HWY/TRAFFIC-ROADWAY/speed_zone_program.shtmlhttp://www.oregon.gov/ODOT/HWY/TRAFFIC-ROADWAY/speed_zone_program.shtmlhttp://www.oregon.gov/ODOT/HWY/TRAFFIC-ROADWAY/speed_zone_program.shtmlhttp://www.oregon.gov/ODOT/HWY/TRAFFIC-ROADWAY/speed_zone_program.shtml


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1. The gap between design speed and desired operatingspeed.

Drivers usually make speed decisions based on the designspeed of the road, not the posted speed. This is significant

because design speed is almost always set higher than thedesired operating speed, the speed that is appropriate to theroads context. This is intended, under our currenttransportation planning paradigm, to be a kind of a safetyallowance for vehicles; if the driver goes a little faster than isreasonable, the road can accommodate that. Engineersfrequently set the design speed at 5 to 10 mph over theexpected operating speed, which means they are designingthe road to be safely driven at 5 mph faster than the speedat which 85% of users are expected to drive (PPS 2008).When the roadway is signaling drivers that they can safelydrive faster than the posted speed, it is not surprising that

drivers often choose to speed.

Some jurisdictions are changing the way they address speedwhen they build roadways. The Smart TransportationGuidebook (2008) recommends that most types of roadwaysbe designed with the goal of making the design speed,operating speed, and the posted speed all the same. TheNew Jersey DOT and Pennsylvania DOT require streets tobe planned with design speeds equal to desired operatingspeeds, and the Vermont Agency of Transportation allows aroadways design speed to be equal to or less than theposted speed (PPS 2008). America Walks stronglyrecommends that American roads be designed and builtwith the explicit goal of setting design speed equal toposted speed and operating speed. This approach willallow for traffic flow while creating a safer, morewelcoming environment for all road users.

2. Reliance on 85th percentile for evaluating changes tospeed limits

Many communities have issues with existing roadwayswhere posted speeds are inappropriately high for thecontext, creating an unsafe environment for road users.

When a roadway is under review for a possible speed limitchange, many states require that the 85th percentile speedbe a major factor in establishing posted speed. The problemwith this is that drivers make choices that seem reasonablebased on the cues they get from the roadway, rather than onwhat they would think to be reasonable if they spent sometime in the community. This creates a feedback loop in whichengineers create roads that cue drivers that they can safelygo faster than the posted speed, and then engineers use

What about the GreenBook?

The Green Book issometimes consideredto be the last word in

road design; itsstandards are oftenadopted wholesale bystates, and the FederalHighway Administrationhas adopted parts of theGreen Book as thestandard for the NationalHighway System.

However, it is worthnoting that the Green

Book was initiallycreated as a designguideline for state DOTsdesigning federallyfunded highways, whichare typically rural. It hasonly recently beenadapted for urbanconsiderations such assurrounding land use,and it remains weak onurban contexts.

Furthermore, the GreenBook is intended toprovide guidance only,and is not a regulatorydocument. It is actuallysomewhat flexible onspeed ranges, and manyengineers haveexercised professionaldiscretion in designingnew or redesign existingstreets with traffic

calming measures toreduce automobilespeeds (often whilemaintaining or improvingtraffic flow).


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those drivers speed choices to indicate what is a reasonable speed to drive on that road.

Many states allow the use of additional factors to determine an appropriate speed limit, thoughalmost all weigh the 85th percentile most heavily. Other factors that may be considered include:

Road type and condition Crash history

Location and type of access points Existing traffic control devices Sight distances Traffic volumes Lane and shoulder width Test run speed Parking practices Pedestrian activity Land use

In the interest of increasing traffic safety, state DOTs should be encouraged, to the

extent possible, to weigh these other factors more heavily than the 85th percentile.

3. The assumption that higher design speed makes roads safer

Road design elements that contribute to higherdesign speed include wide lanes, long sightlines,wide shoulders, and other factors that are intended tobe forgiving in the case of random driver error. Forexample, many engineers believe that one way tomake a road safer is to remove objects from theroadside to create a clear zone so that a car leavingthe roadway is less likely to run into anything(Dumbaugh& Li 2011). The Green Book includes thestatement that every effort should be made to useas high a design speed as practical in the interests ofsafety (AASHTO 2004, p. 67 as cited in Dunbaugh &Li, 2011).

This emphasis on reducing the effects of a crash onthe vehicle and its occupants does nothing to reducethe effects of the crash on people and things outsidethe car, and does nothing to prevent the crash fromhappening in the first place. Furthermore, in urbanareas, crashes happen predictably more often in places where there are relatively higher trafficspeeds, and more conflicts between roadway users (Dumbaugh& Li 2011). Road designshould aim to prevent crashes through reduction of speed, particularly around

intersections, rather than mitigating the effects of crashes on vehicle occupants. Thisapproach is common in European cities, and there are many proven, effective toolsavailable.

4. The prioritization of automobile mobility goals over other community goals

The way our streets are currently designed prioritizes higher speeds over other communitygoals, such as the economic development of individual streets and neighborhoods, safe accessfor people walking to destinations and transit, activating public spaces, and childrens safety. In


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this paradigm, any delay for motor vehicles is a sign of failure. For example, Level of Service,a key measure of a roadways effectiveness, measures the level of congestion at peak times.This measure does not reflect considerations such as the ability of residents to get around(people on foot or bicycles are not as affected by motor vehicle congestion), freight movement,the ability of pedestrians to cross the street safely, or economic activity. In fact, traffic

congestion can even be a positive indicator of a communitys economic vitality (Taylor, 2002.)We should prioritize safety, comfort, economic and social sustainability, and publichealth, and let motor vehicle mobility take its correct place as an element of thetransportation system, rather than its primary goal.

5. Belief in design immunity

While it is extremely unlikely that any liability issues will arise from traffic calming measures,liability issues are often cited as a reason not to pursue any engineering measures perceived asoutside the standard practice. Many engineers feel that they are vulnerable to liability forroadway collisions if they stray from the Green Books guidance, which they perceive as a goodway to get design immunity for roadway design. While this is by no means the only way forengineers and governments to protect themselves from liability, it is an easy, cheap way todesign roads that are legally defensible. Creating original design solutions that are protectedfrom liability requires substantial knowledge, time, and financial resources that many

jurisdictions lack (Urgo et al 2010). As we advocate for lower speeds, we need to find waysto support engineers to explore and use a wider variety of design tools.

What Next?

Communities across the country are eager to move toward traffic speeds that promote safety,access, public health, and economic and social sustainability. We must address theperceptions and practices of transportation professionals that prevent implementation of lowerspeeds.

A lot of work remains to be done on this issue, but America Walks has identified a few changeswe can call for in the transportation profession:

Do slower speeds mean longer travel times?

For communities overall, the minimal added travel time associated with reducing speed ismuch outweighed by the reduced risk of crashes (Archer et al 2008). However, this is adifficult argument to make to people who are concerned only about their individual traveltime. The fact is, though, that for many urban trips, speed limits and even maximumspeed traveled do not have much impact on overall travel time. A car trip on urban streetsis likely to be slowed by many factors, such as signal timing, number and type ofintersections, or trouble finding parking, and travel times tend to be extremely variable. Atrush hour in many cities, the average travel speed is significantly below speed limits,often hovering around 15 mph. Furthermore, lower speeds mean fewer crashes, andfewer crashes means less delay. Crashes are not only devastating for the people who

are directly affected, and costly to society, they are a major cause of traffic jams (FHWA2005). If a system is carefully designed to maintain a slow (20 mph), fairly steady drivingspeed, without a lot of stopping and starting, it can actually improve traffic flow, potentiallyreducing travel times (Archer et al, 2008). Improving intersection safety and function andadjusting signal timing are better ways to improve flow than increasing traffic speed.
http://www.monash.edu.au/muarc/reports/muarc276.pdfhttp://www.monash.edu.au/muarc/reports/muarc276.pdfhttp://www.monash.edu.au/muarc/reports/muarc276.pdfhttp://ops.fhwa.dot.gov/congestion_report/http://ops.fhwa.dot.gov/congestion_report/http://ops.fhwa.dot.gov/congestion_report/http://ops.fhwa.dot.gov/congestion_report/http://ops.fhwa.dot.gov/congestion_report/http://ops.fhwa.dot.gov/congestion_report/http://www.monash.edu.au/muarc/reports/muarc276.pdfhttp://www.monash.edu.au/muarc/reports/muarc276.pdfhttp://www.monash.edu.au/muarc/reports/muarc276.pdfhttp://www.monash.edu.au/muarc/reports/muarc276.pdfhttp://www.monash.edu.au/muarc/reports/muarc276.pdfhttp://www.monash.edu.au/muarc/reports/muarc276.pdf


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Broadly adopt the idea that design speed should be set equal to desired operating speedin all road design;

Deprioritize the 85th percentile rule in setting speed limits; Change the language in the Green Book and other influential design documents that

equate quality with high design speed; and

Research the real impacts of implementing lower speeds on arterials and urban

highways, with an emphasis on maximizing flow while minimizing crashes

These ideas are a starting point. America Walks welcomes ideas and feedback as we moveforward.

ReferencesAmerican Association of State Highway and Transportation Official. 2004. A Policy on

Geometric Design of Highways and Streets.

Archer, Jeffery, Fotheringham, Nicola, Symmons, Mark, and Bruce Corben. 2008. The Impact of

Lowered Speed Limits in Urban and Metropolitan Areas. Transport Accident

Commission Report #276. Accessed 9/23/2011 at

http://www.monash.edu.au/muarc/reports/muarc276.pdf

Dumbaugh, Eric and Li, Wenhao. 2011.Designing for the Safety of Pedestrians, Cyclists, and

Motorists in Urban Environments. Journal of the American Planning Association, 77: 1,

69 8

Federal Highway Administration. 2005.Traffic Congestion and Reliability: Trends and Advanced

Strategies for Congestion Mitigation. Accessed 9/23/2011 at

http://ops.fhwa.dot.gov/congestion_report/

Fitzpatrick Kay, Paul Carlson, Marcus Brewer, Mark Wooldridge, and Shaw-Pin Miaou. 2003.

National Cooperative Highway Research Program Report 504: Design Speed, Operating

Speed, and Posted Speed Practices. Transportation Research Board. Accessed

8/28/2011 athttp://onlinepubs.trb.org/onlinepubs/nchrp/nchrp_rpt_504.pdf Institute of Transportation Engineers. 2006.Context Sensitive Solutions in Designing Major

Urban Thoroughfares for Walkable Communities. Accessed 8/28/2011 at

http://www.ite.org/bookstore/RP036.pdf

Rosen, Erik, and Ulrich Sander. 2009. Pedestrian fatality risk as a function of car impact speed.

Accident Analysis and Prevention 41 (2009) 536542.

Taylor, Brian. 2002. Rethinking Congestion. Access.

Tefft, Brian. 2011. Impact Speed and a Pedestrians Risk of Severe Injury or Death. AAA

Foundation for Traffic Safety. Accessed 10/2/2011 at

http://www.aaafoundation.org/pdf/2011PedestrianRiskVsSpeed.pdf

Toth, Gary, and Wilhelm Volk. 2008.A Citizens Guide to Better Streets: How to Engage Your

Transportation Agency. Project for Public Spaces, Inc. Accessed 8/28/2011 at

http://www.pps.org/pdf/bookstore/How_to_Engage_Your_Transportation_Agency_AARP

.pdf

Urgo, John, Meredith Wilensky, and Steven Weissman. 2010.Moving Beyond Prevailing StreetDesign Standards: Assessing Legal and Liability Barriers to More Efficient Street Designand Function. The Center for Law, Energy, and the Environment, Berkeley Law School,University of California. Accessed 8/28/2011 at
http://www.monash.edu.au/muarc/reports/muarc276.pdfhttp://www.monash.edu.au/muarc/reports/muarc276.pdfhttp://www.peoplepoweredmovement.org/site/images/uploads/931668506.pdfhttp://www.peoplepoweredmovement.org/site/images/uploads/931668506.pdfhttp://www.peoplepoweredmovement.org/site/images/uploads/931668506.pdfhttp://www.peoplepoweredmovement.org/site/images/uploads/931668506.pdfhttp://ops.fhwa.dot.gov/congestion_report/http://ops.fhwa.dot.gov/congestion_report/http://ops.fhwa.dot.gov/congestion_report/http://ops.fhwa.dot.gov/congestion_report/http://ops.fhwa.dot.gov/congestion_report/http://ops.fhwa.dot.gov/congestion_report/http://onlinepubs.trb.org/onlinepubs/nchrp/nchrp_rpt_504.pdfhttp://onlinepubs.trb.org/onlinepubs/nchrp/nchrp_rpt_504.pdfhttp://onlinepubs.trb.org/onlinepubs/nchrp/nchrp_rpt_504.pdfhttp://onlinepubs.trb.org/onlinepubs/nchrp/nchrp_rpt_504.pdfhttp://onlinepubs.trb.org/onlinepubs/nchrp/nchrp_rpt_504.pdfhttp://onlinepubs.trb.org/onlinepubs/nchrp/nchrp_rpt_504.pdfhttp://www.ite.org/bookstore/RP036.pdfhttp://www.ite.org/bookstore/RP036.pdfhttp://www.ite.org/bookstore/RP036.pdfhttp://www.ite.org/bookstore/RP036.pdfhttp://www.ite.org/bookstore/RP036.pdfhttp://www.ite.org/bookstore/RP036.pdfhttp://www.aaafoundation.org/pdf/2011PedestrianRiskVsSpeed.pdfhttp://www.aaafoundation.org/pdf/2011PedestrianRiskVsSpeed.pdfhttp://www.pps.org/store/books/a-citizens-guide-to-better-streets-how-to-engage-your-transportation-agency/http://www.pps.org/store/books/a-citizens-guide-to-better-streets-how-to-engage-your-transportation-agency/http://www.pps.org/store/books/a-citizens-guide-to-better-streets-how-to-engage-your-transportation-agency/http://www.pps.org/store/books/a-citizens-guide-to-better-streets-how-to-engage-your-transportation-agency/http://www.pps.org/store/books/a-citizens-guide-to-better-streets-how-to-engage-your-transportation-agency/http://www.pps.org/pdf/bookstore/How_to_Engage_Your_Transportation_Agency_AARP.pdfhttp://www.pps.org/pdf/bookstore/How_to_Engage_Your_Transportation_Agency_AARP.pdfhttp://www.pps.org/pdf/bookstore/How_to_Engage_Your_Transportation_Agency_AARP.pdfhttp://crec.berkeley.edu/Moving%20Beyond%20Prevailing%20Standards.pdfhttp://crec.berkeley.edu/Moving%20Beyond%20Prevailing%20Standards.pdfhttp://crec.berkeley.edu/Moving%20Beyond%20Prevailing%20Standards.pdfhttp://crec.berkeley.edu/Moving%20Beyond%20Prevailing%20Standards.pdfhttp://crec.berkeley.edu/Moving%20Beyond%20Prevailing%20Standards.pdfhttp://crec.berkeley.edu/Moving%20Beyond%20Prevailing%20Standards.pdfhttp://crec.berkeley.edu/Moving%20Beyond%20Prevailing%20Standards.pdfhttp://crec.berkeley.edu/Moving%20Beyond%20Prevailing%20Standards.pdfhttp://crec.berkeley.edu/Moving%20Beyond%20Prevailing%20Standards.pdfhttp://crec.berkeley.edu/Moving%20Beyond%20Prevailing%20Standards.pdfhttp://crec.berkeley.edu/Moving%20Beyond%20Prevailing%20Standards.pdfhttp://crec.berkeley.edu/Moving%20Beyond%20Prevailing%20Standards.pdfhttp://crec.berkeley.edu/Moving%20Beyond%20Prevailing%20Standards.pdfhttp://crec.berkeley.edu/Moving%20Beyond%20Prevailing%20Standards.pdfhttp://crec.berkeley.edu/Moving%20Beyond%20Prevailing%20Standards.pdfhttp://crec.berkeley.edu/Moving%20Beyond%20Prevailing%20Standards.pdfhttp://crec.berkeley.edu/Moving%20Beyond%20Prevailing%20Standards.pdfhttp://crec.berkeley.edu/Moving%20Beyond%20Prevailing%20Standards.pdfhttp://crec.berkeley.edu/Moving%20Beyond%20Prevailing%20Standards.pdfhttp://crec.berkeley.edu/Moving%20Beyond%20Prevailing%20Standards.pdfhttp://crec.berkeley.edu/Moving%20Beyond%20Prevailing%20Standards.pdfhttp://crec.berkeley.edu/Moving%20Beyond%20Prevailing%20Standards.pdfhttp://crec.berkeley.edu/Moving%20Beyond%20Prevailing%20Standards.pdfhttp://crec.berkeley.edu/Moving%20Beyond%20Prevailing%20Standards.pdfhttp://crec.berkeley.edu/Moving%20Beyond%20Prevailing%20Standards.pdfhttp://crec.berkeley.edu/Moving%20Beyond%20Prevailing%20Standards.pdfhttp://crec.berkeley.edu/Moving%20Beyond%20Prevailing%20Standards.pdfhttp://crec.berkeley.edu/Moving%20Beyond%20Prevailing%20Standards.pdfhttp://crec.berkeley.edu/Moving%20Beyond%20Prevailing%20Standards.pdfhttp://crec.berkeley.edu/Moving%20Beyond%20Prevailing%20Standards.pdfhttp://crec.berkeley.edu/Moving%20Beyond%20Prevailing%20Standards.pdfhttp://crec.berkeley.edu/Moving%20Beyond%20Prevailing%20Standards.pdfhttp://crec.berkeley.edu/Moving%20Beyond%20Prevailing%20Standards.pdfhttp://crec.berkeley.edu/Moving%20Beyond%20Prevailing%20Standards.pdfhttp://crec.berkeley.edu/Moving%20Beyond%20Prevailing%20Standards.pdfhttp://crec.berkeley.edu/Moving%20Beyond%20Prevailing%20Standards.pdfhttp://crec.berkeley.edu/Moving%20Beyond%20Prevailing%20Standards.pdfhttp://crec.berkeley.edu/Moving%20Beyond%20Prevailing%20Standards.pdfhttp://crec.berkeley.edu/Moving%20Beyond%20Prevailing%20Standards.pdfhttp://crec.berkeley.edu/Moving%20Beyond%20Prevailing%20Standards.pdfhttp://www.pps.org/pdf/bookstore/How_to_Engage_Your_Transportation_Agency_AARP.pdfhttp://www.pps.org/pdf/bookstor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