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From Highway to My Way

By Reid Ewing

You know the world is changing when everyone from the Federal Highway Administration to state and local transportation officials uses words such as "flexible" and "context sensitive" to describe highway design. Now that the nation's highways are nearly complete, transportation professionals are turning their sights on local communities and the inherent links between transportation systems and surrounding land uses.

There is a lot of confusion about exactly what constitutes context-sensitive highway design, what latitude exists under current standards and guidelines, what tort liability attaches to such efforts, and what effect context-sensitive designs will have on traffic safety and service levels. This article seeks to sort out myth from fact.

Main Street Destroyed

In the course of writing Best Development Practices (APA Planners Press, 1996), I visited every medium-sized town with any historic character in the state of Florida. I was on a quest for the best traditional small towns in the state, hoping to find lessons applicable to contemporary development projects. Unfortunately, I found very few good examples, mostly because of what was happening along Main Street.

Main Street, usually part of the state highway system, no longer functioned as a comfortable shopping street. It was too wide, and on-street parking had been removed, street trees replaced with asphalt, and sidewalks narrowed. Strip commercial development seemed the only practical land use. The traditional towns that did end up in the book, such as Dade City, had somehow managed to evade the standard DOT definition of "progress."

The problem of context-insensitive highways is not, of course, unique to Florida, nor to small towns, nor to state highways. Instead of gracious boulevards, avenues, and shopping streets, America's urban areas are criss-crossed by arterials and collectors that move traffic but have no power to move mens' souls.

DOTs vs. dots

Here are several examples proving that change is in the air. U.S. Route 6 narrows to two lanes as it runs through the town of Brooklyn, Connecticut. Sight distance is less than 250 feet at one point, driveways are closely spaced, and there is little roadside clearance should a driver lose control. Yet traffic speeds through the town still range up to 54 mph.

A 1991 state plan sought to correct these dangerous conditions by widening the road to four lanes, straightening the alignment, and adding eight-foot shoulders. The village appealed the plan to the Federal Highway Administration under the National Environmental Policy Act, and the Connecticut Department of Transportation was sent back to the drawing board. ConnDOT's next proposal was a bypass around the town, which was also rejected. Finally, after years of additional planning, a compromise was reached in 1998. It keeps the existing alignment through the town center, retains the two-lane cross section, adds narrow shoulders and sidewalks, and realigns the road marginally at the most dangerous curve. Reconstruction will be completed in 2003.

In Anchorage, Alaska, engineers proposed the conversion of 15th Avenue into a one-way couplet with 14th Avenue after a safety study documented high accident rates and substandard geometrics. However, residents of the adjacent Rogers Park neighborhood had seen one-way couplets in operation in midtown, and this was exactly what they didn't want. The couplets moved traffic efficiently but divided the community much as a freeway would.

And so began a four-year process of redesign that in 1998 resulted in a four-lane, tree-lined boulevard on the east end, and a narrowed three-lane cross section on the west. When construction is completed later this year, lanes will be maintained at their current 11-foot width, and shoulders excluded. Instead of a shoulder, a wide gutter pan will provide a refuge area and bike-friendly surface. Sidewalks will be set back from the street for the first time.

photo: East Main Street in Westminster, Maryland.

East Main Street in Westminster, Maryland, after reconstruction. The community avoided widening the road and eventually took over its operation and maintenance. Hundreds of street trees, midblock crosswalks, and other amenities were installed. (photo: Maryland State Highway Administration)

In Westminster, Maryland, the base layer of East Main Street needed reconstruction, underground utility lines had to be replaced, and the storm drain system needed upgrading. After checking the Maryland Roadway Design Manual, the district engineer proposed widening the road to 40 feet. Widening would have provided 12-foot travel lanes and eight-foot parking lanes on each side. It also would have eliminated nearly all street trees and reduced the sidewalk width to two feet in places.

After learning about the widening, a local resident began a campaign to preserve the street's historic character. She appealed to the mayor, who convinced the Maryland State Highway Administration to reconstruct within the street's existing dimensions. The result is a classic main street with "bulb out" curb extensions at intersections, midblock crosswalks, hundreds of additional street trees, and brick surfacing in the crosswalks.

In these and many other cases uncovered in our research, the need for road improvements was undeniable, but standard design solutions were unacceptable to the people most affected by them-those along the right-of-way. The resulting tension between DOT and community goals led to compromise and context-sensitive designs.

Reform at the Top

Before 1991, all roads built in the U.S. and paid for even in part with federal funds had to meet guidelines in the American Association of State Highway and Transportation Officials (AASHTO) "Green Book" (A Policy on Geometric Design of Highways and Streets). If officials wanted to do something different, their only options were to seek design exceptions from the Federal Highway Administration or to build entirely with state and local funds.

The Intermodal Surface Transportation Efficiency Act of 1991 (ISTEA) changed all that by creating a National Highway System made up of the interstate system and other high-performance state highways, 160,000 miles of roadway in all. Other roads became eligible for federal funding under a separate surface transportation program. For roads not on the NHS, ISTEA gave states latitude to adopt alternative design, safety, and construction standards.

ISTEA was followed by two other milestones. The National Highway System Act of 1995 provided that even NHS highways (other than interstate highways) could be designed to take into account the environmental, scenic, aesthetic, historic, community, and preservation impacts of any proposed activity. Two years later, the Federal Highway Administration published Flexibility in Highway Design, which forcefully advocates flexible design of highways running through communities, encouraging highway designers to exercise flexibility within existing AASHTO guidelines.

Reform in the States

At the state level, much of the effort to promote context sensitivity has been process and people-oriented. Five states (Connecticut, Kentucky, Maryland, Minnesota, and Utah) are participating in a joint FHWA/AASHTO effort to train engineers in context-sensitivity through the National Cooperative Highway Research Program (NCHRP). Many states, including New Jersey, have launched training efforts of their own. The New Jersey training consists of five day-long sessions on such unconventional topics (at least for highway engineers) as placemaking, respectful communication, and negotiation and conflict management.

While such efforts are laudable, they inevitably run up against engineering constraints unless DOT standards and policies are revised. Michael King, a consultant on the NJDOT flexible highway design project, surveyed more than a dozen states to find out about their efforts to develop new standards and policies. Substantive changes are happening at the state level now.

Don't Blame the Green Book

King found that few states have adopted sub-AASHTO geometric standards. Among those that have, deviations from Green Book values are relatively slight. The difference between the cross sectional width of a two-lane urban arterial under Vermont's much heralded design standards and that under the Green Book minimums is only three feet (43 vs. 46 feet). Notably, Dave Scott, director of project development and keeper of the Vermont standards, has advised our New Jersey study team not to recommend anything less than AASHTO minimums because there is little to gain on urban main streets.

This is not to say that the AASHTO Green Book is without shortcomings. Its design guidelines are often based on studies dating from a time when tires, braking systems, pavements, and vehicle dimensions were less forgiving than today's. However, these guidelines mostly affect the design of high-speed rural roads. The issue in the New Jersey study is whether good urban streets can be accomplished under AASHTO guidelines.

Here are some of the AASHTO guidelines for urban arterials:

  • Design speed. AASHTO allows design speeds as low as 31 mph in central business districts and intermediate areas. Posted speeds would ordinarily be considerably lower.
  • Lane width. The minimum lane width is 9.8 feet for urban arterials with little or no truck traffic. A minimum of 10.8 feet is prescribed for general traffic on urban arterials designed for speeds up to 37 mph.
  • Setback of street trees. On curbed sections, the minimum clearance from the curb face is 1.6 feet. A 3.3-foot clearance is considered desirable, particularly near intersections and driveways where turning vehicles may overhang the curb.
  • Midblock crosswalks. AASHTO is neutral on these.
  • On-street parking. Parallel parking is allowed where adequate street capacity is available.
  • Corners. Corner radii of 9.8 to 13.7 feet are reasonable under constrained conditions. On arterials carrying high volumes, larger radii are recommended (in some cases, much larger) to facilitate turns to and from the through lanes.
  • Pedestrian refuge islands. Median islands are encouraged where space permits.
  • Sidewalks. The minimum border width, including sidewalk and planting strip, is 7.9 feet; 11.8 feet is preferred.
  • Barrier curbs. Barrier curbs are encouraged in areas of high pedestrian traffic and speeds up to 37 mph, or on discretionary basis, up to 50 mph. At higher speeds, barrier curbs do not act as barriers anyway.

The conclusion: It appears that we cannot place too much blame on the Green Book for the sorry state of urban streets.

Liability Isn't the Issue, Either

Governments used to have general immunity from tort liability, but that has changed since the 1960s, as various courts and legislatures made it possible for individuals and groups to sue in cases where government fails to exercise due care in its decisions.

Government decisions are now divided into two classes: discretionary (planning decisions) and ministerial (operational decisions). Discretionary decisions involve a choice among valid alternatives and are generally immune from tort claims. Ministerial decisions leave minimal leeway for personal judgment and are not immune.

As part of our study for New Jersey DOT, we surveyed statutory and recent case law in 16 states. With the sole exception of local roads in Vermont, all states had replaced sovereign immunity with more limited discretionary immunity.

New Jersey has a Tort Claims Act that leaves the state almost completely immune from tort liability resulting from design-related decisions. All it takes is for the right body or person to approve a design (or the standards on which a design is based).

At the other extreme is Georgia, whose supreme court held in DOTv. Brown (1996) that the design of a roadway is an operational function, not covered by discretionary immunity: "Only the decision to build, and not where or how it is built, is immune." Between these extremes are states such as California and South Carolina, which provide design immunity but allow it to lapse as conditions change. From our 16-state survey, we don't find tort liability much of an excuse for the sorry state of urban streets. Instead, we have identified some real culprits.

Put the Blame Here

The AASHTO Green Book offers design policies and guidelines, not standards. For each design element, AASHTO typically provides a range of acceptable values, from a minimum value to a more desirable target value.

For an AASHTO guideline to become a standard, it must be adopted by a responsible agency. Many states have adopted standards toward the middle or upper end of the AASHTO ranges, on the theory that if some is good, more is better. County and city engineers have then blindly adopted state standards.

As noted, Maryland's lane width standards would have encroached on trees and sidewalks in the town of Westminster. Those standards exceeded AASHTO minimums. Not only were these particular standards thrown out, but the experience convinced Bob Douglass, the Maryland State Highway Administration's deputy chief engineer, that the standards should be thrown out wholesale.

In 1998, Douglass wrote a memo banning the use of the state's highway design manual. He found that the templates were generally oversized (especially stopping sight distance and vertical curves) and stymied creativity among engineers. The agency was losing legal challenges when an element was below the state minimum value, but above the Green Book value. Now the agency relies exclusively on the Green Book.

In the Wrong Class

Another culprit is misclassification of streets. Streets and highways in this country are classified by location-urban or rural-and by function: arterial, collector, and local. There is a direct relationship between classification and design standards. Classification determines design speed, design vehicle, and cross section (lane width, shoulder width, and type and width of median).

The U.S. classification system has been criticized for ignoring distinctions among contexts and among roadway functions. An urban arterial conforms to the same basic standards whether it is a main street or a bypass.

Misclassification of streets commonly occurs for two reasons. A small town, village, or hamlet fails to meet the census definition of metropolitan area urban because it lacks a population of at least 50,000 and a density of at least 1,000 persons per square mile. That community may end up with a main street designed to rural standards. This was true in Brooklyn, Connecticut, before the compromise described at the beginning of this article. The simple solution to this problem is to treat any place that is built up as urban, regardless of its census designation. The Federal Highway Administration policy is simple: If it looks urban, use urban standards.

The other common case of misclassification occurs as road functions change over time. In Westminster, Maryland, East Main Street had always been part of Maryland State Route 32. It began functioning more like a local street when the State Road 140 bypass opened. Accordingly, this portion of Route 32 was removed from the Maryland state highway system after the street was reconstructed, and the city assumed responsibility for its operation and maintenance. Other examples of de-designation include Sunset Drive in South Miami and Springfield Avenue (N.J. Route 124) in Maplewood, New Jersey.

Level of Disservice

Level-of-service standards are yet another cause for concern. While there is a legal imperative to provide safe roads, there is no such reason to provide free-flowing roads. Some congestion may be desirable in a downtown. After all, a downtown without traffic isn't a very exciting downtown.

Virtually all DOTs have adopted level-of-service standards. Typically, the standard for urban areas is C or D, while the standard for suburban areas is B or C. As traffic volumes increase to the point where the standard is no longer met, a road and its intersections often will be widened regardless of the effects on adjacent land uses.

The alternative is to accept congestion in areas that function as destinations. Since 1993, Florida has allowed its local governments to exempt streets through downtowns and urban redevelopment areas from level-of-service standards. The effective standard becomes level-of-service F. Many cities and towns have taken this option.

West Palm Beach, for example, has adopted level-of-service E as its standard and is seeking a complete exemption from level-of-service standards for muchof the city. This city keeps an eye on both low volume-to-capacity ratios (less than 0.6) and high ones (greater than 0.9). A low volume-to-capacity ratio may offer an opportunity-a place where the street can be narrowed and street life encouraged by means of widened sidewalks, on-street parking, and landscaped curb extensions and islands.

photo: Intersection in Dade County, Florida

Dade County, Florida (photo: Reid Ewing)

It is worth noting that several of the context-sensitive projects we studied have improved or at least maintained roadway level-of-service despite narrowed roadways. How? Through clever treatment of intersections, where most delays occur.

The Standard Cross-Section

Nearly all state DOTs include typical sections-another culprit-in their road design manuals. If an area is classified as urban, and a road is functionally classified as a principal arterial, the typical section for an urban principal arterial becomes the default roadway. Typical sections inhibit flexible and context-sensitive design in two ways. First, where right-of-way is constrained, something must be sacrificed to maintain standard travel lane widths: it is usually the sidewalk, landscape buffer, parking lane, or bike lane. Also, there is the tendency to adopt a single, typical section for an entire stretch of road, even when conditions change along its length. Having a single typical section is convenient for the design engineer and construction crew, but it is not good policy.

A dramatic example, to be featured in our upcoming guidebook for New Jersey DOT, is found in Saratoga Springs, New York. South Broadway (U.S. 9) changes from a four-lane, semi-rural highway with a striped median and posted speed of 55 mph to a three-lane urban road with a raised median, single northbound lane, and posted speed of 30 mph, all in a stretch of 1,800 feet.

By all accounts, the section in question would have been reconstructed as a uniform four-lane road, but for two things. First, in 1999, the New York State DOT started an environmental initiative, with context-sensitive design at its heart. Second, the highway passes Saratoga Spa State Park, the Lincoln Baths, and the Museum of Dance. Something special, more like a gateway, was required. Ultimately, a series of roadway sections got built that make a smooth transition from the high-speed semi-rural environment to the south to the low-speed urban environment to the north.

photo: U.S. 9 in Sarasota Springs, New York.

photo: U.S. 9 in Sarasota Springs, New York.

photo: U.S. 9 in Sarasota Springs, New York.

In Sarasota Springs, New York, U.S. 9 changes from a four-lane, semi-rural highway with a 55 mph speed limit to a three-lane urban road with a 30 mph speed limit, all within a stretch of 1,800 feet. (photos: Reid Ewing)

In Westminster, Maryland, the base layer of East Main Street needed reconstruction, underground utility lines had to be replaced, and the storm drain system needed upgrading. After checking the Maryland Roadway Design Manual, the district engineer proposed widening the road to 40 feet. Widening would have provided 12-foot travel lanes and eight-foot parking lanes on each side. It also would have eliminated nearly all street trees and reduced the sidewalk width to two feet in places.

The Three Rs

At least in theory, roads that are being resurfaced, restored, or rehabilitated (so-called 3R projects) do not have to be upgraded to current geometric standards. In some states, 3R projects are instead subject to special standards below those of AASHTO-with the blessing of the Green Book. By contrast, under state and federal policies, roads reconstructed down to their bases must be brought up to current standards.

In a constrained main street environment, there is no reason to treat 3R and reconstruction projects differently. In both cases, designers already know how a road performs based on historical accident and other data. The Maryland State Highway Administration reached this conclusion recently, and now leaves existing cross sections alone unless there is a documented crash problem.

Exceptions to the Rules

The Federal Highway Administration grants design exceptions on the National Highway System, and the same is true for state or local DOTs on non-NHS roads. Between 1997 and 1999, New Jersey DOT engineers requested and received design exceptions for 81 projects, including most major highway projects undertaken by the state.

From our review of the 81 reports, exceptions were commonly granted for substandard shoulder width, substandard banking on horizontal curves, and substandard stopping sight distance on vertical curves. The process appears flexible - but exceptions are typically requested in order to save money, not to preserve context.

Here is a typical scenario: A road is being reconstructed, and a sharp curve must be straightened to meet the standard for horizontal curvature. However, someone's house or business would be taken, some park or cemetery would be encroached on, a lot ofextra asphalt would have to poured, or some other big expense would be incurred.

And so the design engineer checks accident statistics for the location in question, focusing on the types of accidents associated with substandard horizontal curves, and finds that the curve in question generates only an average number of accidents compared to state norms. Noting that substantial costs can be avoided by allowing a substandard horizontal curve, a design exception is requested and granted.

Sometimes context also is taken into account, as with a road and bridge project in an historic district of Oxford Township, New Jersey. But that is a rare occurrence.

Let's Use Common Sense

Gary Toth, one of the overseers of our research at New Jersey DOT, keeps saying that context sensitive design is just a matter of common sense. If the designer understands the transportation context, and the safety and mobility needs to be addressed, and then uses common sense to fit sound engineering principles into the environmental and community context, a design will emerge that represents the best of both worlds.

On 15th Avenue in Anchorage, Alaska, the first common sense decision was to divide the roadway section into three segments because traffic turns off as it heads west. Daily volumes drop from 22,000 at one end of the avenue to 4,000 at the other, implying very different cross sections. Focusing on the westernmost segment, the second common sense decision was to drop a lane, from four to three, the center lane becoming a continuous left-turn lane.

In a third common sense decision, the top westbound lane was replaced with a five-foot sidewalk and landscape buffer between the road and sidewalk. By reducing the number of lanes, the state is also reducing the amount of snow to be cleared, and creating more storage space for it in the landscape buffer. With Anchorage's low sun angle, and the sun blocked by buildings and trees, the engineers expect that three additional weeks of bare pavement a year will result from the decision to place the sidewalk on the north side of the street rather than dropping an eastbound lane and placing the sidewalk on the south side.

The final exercise of common sense was to seek several design exceptions. Some stopping and intersection sight distances, curb return radii, shoulder widths, and clearances to obstructions will remain substandard. However, the project will still improve safety and, with the design exceptions in place, cost about a third as much.

What's Next

Because AASHTO has been responsible for, or at least been blamed for, so much of what of what we don't like about urban streets in this country, it seems fitting to end on a positive note from an AASHTO draft document, scheduled for publication soon.

"The notion of designing a 'high quality,' low speed road is counter intuitive to many highway engineers, yet it is in many cases the appropriate solution. . . . Context sensitive design in the urban environment often involves creating a safe roadway environment [by encouraging drivers] to operate at low speeds."

This document offers a qualified endorsement of traffic calming, something unimaginable five years ago.

Reid Ewing is a Research Professor at Rutgers University and Research Director of the Surface Transportation Policy Project in Washington, D.C. He teaches Traffic Calming for Tech Transfer. This article is an outgrowth of the Flexible Design Standards for Communities project, conducted by Rutgers University under contract with the New Jersey Department of Transportation. Reid can be reached at


Flexibility in Highway Design, Federal Highway Administration, Washington, D.C., 1997.

"Building Roads in Sync With Community Values," by Harold Peaks and Sandra Hayes, Public Roads, FHWA, March/April 1999.

Creating Livable Streets: Street Design Guidelines for 2040, Portland Metro, Portland, Oregon, 1997.

Traditional Neighborhood Development (TND) Guidelines, North Carolina DOT, Raleigh, North Carolina, 2000.

Main Street-When a Highway Runs Through It: A Handbook for Oregon Communities, Oregon DOT, Salem, 1999.

Take Back Your Streets: How to Protect Communities from Asphalt and Traffic, Conservation Law Foundation, Concord, NH, 1998.

Traffic Calming: State-of-the-Practice, by Reid Ewing, Institute of Transportation Engineers, 1999.