Slow ride: calming traffic
Prosperity often comes with a price. A booming economy, rapid urban growth and the resulting heavy traffic frequently make streets less hospitable to pedestrians, bicyclists and motorists.
In cities large and small, many families can afford a second or even third car. Flush with cash, consumers drive those cars to places where they can spend money: shopping malls, health clubs, restaurants. Nationwide, roadways are becoming increasingly congested with people who generally are more mobile than their parents were and tend to live miles away from where they work. More and more, pedestrians, bicyclists and homeowners must put up with hyperactive traffic and inconsiderate drivers who seem always to be in a hurry. It can be an annoying – and dangerous – phenomenon.
The answer, many communities are finding, is traffic calming, or using engineering, street design and electronic means to lower traffic speed. Nascent in the United States, traffic calming began more than a quarter century ago in Europe, a land of narrower streets and smaller cars where “walkable” cities are more the norm.
Years ago, “diversion projects” or “neighborhood traffic management” strategies served as passive precursors to traffic calming, according to Jim Ford, vice president of infrastructure services for Long Beach, Calif.-based Earth Tech. Examples include the conversion of streets into one-way thoroughfares, the addition of traffic signals and signs, and the implementation of educational programs.
Over time, traffic engineers have deployed various other tools and techniques to help homeowners take back their neighborhoods. Medians, traffic circles, speed bumps, humps, elevated sidewalks and sidewalk “bulbs” protruding into the street are among the wide arsenal from which traffic engineers can draw. They also can employ high-tech devices such as “photo radars” that check vehicle speeds, record the license plate numbers of violators and automatically issue speeding tickets that will be mailed to the offenders.
According to Washington, D.C.-based Public Technology, Inc., traffic calming steps vary dramatically in cost. Modest efforts such as increased signage, “rumble strips” and narrower lane stripes, may cost a few hundred dollars each; while more elaborate projects such as raised intersections, full medians and traffic circles with landscaping and drainage could exceed $40,000 each.
At least 350 jurisdictions across the country have engaged in traffic calming, according to a study by the University of California at Berkeley. The study, “A Survey of Traffic Calming Practices in the United States,” determined that most localities implement traffic calming on a “location-by-location” basis rather than comprehensively. Furthermore, the study discovered that jurisdictions generally cede much decision-making to residents, and traffic engineering divisions generally are put in charge of running traffic-calming programs. It also concluded that most traffic-calming programs are funded by local governments; few rely on funding from residents; and very few have received state or federal money.
The situation in Portland, Ore., may explain why residents usually are not asked to ante up. After implementing traffic calming in the mid-1980s, the city found that demand for traffic-calming measures exceeded its ability to pay for them. When Portland launched a Residential Speed Bump Purchase Program, many residents did not put their money where their mouths were, and requests for traffic bumps tailed off dramatically.
A variety of factors Traffic calming has become a popular road-building philosophy simply because many homeowners, traffic engineers and city planners have reached an almost unanimous conclusion: There are just too many people driving too many places too fast.
Often, people are stretched to the limit as they race from work to the dry cleaners to soccer practice. They must negotiate the sprawl that typifies so many American cities, trying to reach numerous far-flung destinations in limited time.
The modern subdivision, in which cul-de-sacs proliferate and through streets are few, can exacerbate the problem. The cul-de-sacs, paradoxically, may calm traffic for a subdivision’s residents but worsen it for surrounding streets. Often, only one street leads into and out of a subdivision. That means that, whenever residents leave, they all exit onto the same arterial road or highway.
Besides the roads and sprawl, vehicle design may also contribute to the need for traffic calming. Today’s large vehicles insulate drivers from the road, making them less aware of how fast they are traveling. “The perception of the person in the car is very different [from] the perception of the person on the sidewalk,” says Rochelle Wheeler, associate planner in the Berkeley, Calif., planning and development department.
The irony is that traffic engineers have come full circle in their mission. Thirty or 40 years ago, they focused on building straight, flat and broad roadways free of obstructions, to encourage vehicle movement. Today, however, many of them do just the opposite. A key reason for that is Americans’ long-standing love affair with the automobile.
In fact, many cities have witnessed a significant increase in the number of vehicles per capita since the early 1970s. Research Atlanta, part of Georgia State University’s School of Policy Studies, has found that, since 1970, the 21-county metro Atlanta region has experienced a 134 percent population increase and a 178 percent increase in vehicle registrations. By 1995, the vehicle/population ratio had increased to .89, meaning metro Atlanta has about 3.1 million vehicles crowding its roadways.
Wheeler says the same is true for Berkeley. “What we see here in Berkeley is that there definitely are more cars per capita, and people are driving more,” she says. “That tends to create more congestion on our major streets, which means people are more likely to want to cut through neighborhoods.”
Crime stopper? While traffic calming is intended primarily to slow and thin traffic, local governments may implement it for other reasons as well. For example, public transit facilities and shopping malls often incorporate elements such as lighting, translucent wind screens and landscaping to reduce crime. Traffic calming can provide the same benefits.
Columbus, Ohio, uses traffic calming for conventional reasons but also employs it to put a damper on criminal activities such as drug dealing and prostitution. Three years ago, the city closed alleys, made several other streets one-way and blocked off a major street in the Weinland Park neighborhood near downtown.
The city also blocked three access points at the Big Four Alley near the Ohio State University campus. “The police get fewer complaints now,” reports Susan Watiker, a spokeswoman for the city’s Public Service Department.
Steve Tweed, traffic calming coordinator, lends another perspective. “I don’t know if it solved the problem, but it definitely moved the problem,” he says. Opinions vary on the effectiveness of traffic calming as crime-stopper. In Berkeley, two-thirds of the city’s speed humps were installed to stem drug dealing, drive-by shootings and reckless driving. In an evaluation of the city’s traffic-calming program, Berkeley’s Advance Planning Division concluded, “There is little evidence that [the speed humps] have had an impact on these activities.”
Tweed concurs. “That [prostitution and drug dealing] is more of a social problem and a police problem,” he says. “Engineering can only do so much. My main interest is to slow down the cars.”
Critics’ complaints Police may favor traffic calming if it keeps the anti-social elements off city streets and puts a dent in drug dealing, but they may oppose it if they fear it will inhibit their ability to respond to calls. Law enforcement officials as well as other emergency personnel such as firemen and paramedics are some of the main critics of traffic calming. They note that traffic calming results in speed bumps and humps, barriers and a variety of sidewalk and curb protrusions that can interfere with access and response times. For that reason, city planners would do well to always include fire, medical and other emergency personnel in the planning process.
Boulder, Colo., is a case in point. The city has 28 speed humps raised 5 to 6 inches for 18 to 23 feet; 26 humps that are 3 to 4 inches high for 12 feet; five raised intersections, each 4 to 6 inches high and 40 to 50 feet long; and 12 traffic circles, four of which are temporary. Concrete “parking bumpers” commonly used to divide spaces in parking lots were used for the temporary traffic circles.
In part because of complaints from the fire department, Boulder’s city council last year issued a moratorium on further installation of permanent traffic-calming devices, says Noreen Walsh, a traffic planner with the city. In the meantime, city officials are assessing how to best map out emergency routes and what methods of enforcement, such as photo radar units, are most effective. “We’re looking to go back to the city council in December with some results from our demonstration projects,” Walsh says.
Boulder also is augmenting engineering and technology initiatives with good old-fashioned citizen involvement. Many residents affix stickers to their trash cans promoting safe, courteous driving. They also take a “neighborhood speed pledge” and join in neighborhood speed watches.
Studying response time Berkeley, one of America’s traffic-calming pioneers, has conducted informal studies to determine how much fire engines and ladder trucks are slowed by speed humps. (Unlike speed bumps, commonly used in parking lots and typically having only 10 or 12 inches of raised pavement, speed humps usually feature more of a slope than a bump and have about 12 to 24 feet of pavement that is elevated 4 to 6 inches.)
Wheeler says the Berkeley fire trucks are delayed an average of 10 seconds per 12-foot hump and 3 seconds per 22-foot hump. The difference is largely attributable to the distance between the humps, she says.
The 12-foot humps on the test street were about 200 feet apart, limiting the trucks’ ability to pick up speed between them. By contrast, the 22-foot humps were 330 feet apart, enabling drivers to significantly increase speed between them.
Cities concerned about blocking access to emergency vehicles can follow Columbus’s example. The city designed barriers at Weinland Park so that fire trucks can be driven right through them if necessary.
Concerns about speed humps and other traffic-calming devices involve issues other than emergency response. For example, in northern cities, public works personnel in charge of snow removal may balk at traffic calming, since speed humps, diverters and narrow turning circles are not necessarily snowplow-friendly, according to Robert Hicks, director of transportation for Public Technology, Inc. Bicyclists and persons with spinal injuries or other medical conditions also may object to traffic speed humps and bumps.
Devising a plan Often initiated by a simple call or letter from a citizen or neighborhood group to an elected official, traffic calming is a quintessentially grass-roots issue. That quality ensures citizen involvement yet can confuse city leaders. The problem, says Bill Troe, senior professional associate planner with Omaha, Neb.-based HDR Engineering, is that, often, there is more than one vocal group, each with its own petitions and complaints, and that sends an unclear message to city officials. “The biggest concern is getting consensus in a neighborhood, [and] making sure that the neighborhood can define what the problem is,” Troe says.
“There’s usually a very vocal minority,” says Tweed of Columbus. “They’ll be there every step of the process, saying ‘We don’t feel this is needed.’ But often, the biggest opponents do a ‘180’ and support it once it’s in place.”
To that end, a methodical process involving neighborhood petitions, ballots and public meetings, is essential, says Ford. “When you don’t have some kind of process like that and don’t let the citizens know what’s going to happen up front, it becomes hit or miss.” Typically at the outset, about 65 to 70 percent of a neighborhood’s residents must favor some kind of traffic calming in order for the entire process to unfold.
For several months, Ford has been a consultant to Norwalk, Conn.-based Southwestern Regional Planning Agency, which serves eight cities. His involvement includes meeting with city officials to learn of their concerns; conducting traffic-calming workshops for the public; holding all-day workshops involving professional staff such as engineers, planners, members of city government and other officials; and conducting individual meetings with each of the eight communities.
Armed with all that input, Ford will present a “toolbox” of feasible steps the planning agency could take, as well as advise against other measures deemed impractical or too expensive. Besides seeking input from residents, traffic planners must take other things into consideration, such as state statutes, liability risks and emergency response routes.
Unlike a major street or highway project that cannot be removed once it is put in place, traffic calming allows for inexpensive trial runs before a plan is implemented. “That’s one of the things you can do with traffic calming that makes a lot of sense: Try it out on a temporary basis and see how it works,” Ford says. It could be said that traffic calming offers planners the opportunity to mix and match various elements on a temporary basis until the right recipe is found.
He notes that, while cities can learn from one another to some extent, it is not wise to assume that what works for one city will work for another. “Each project is different, and each project needs to be specially designed,” Ford says.
While the traffic-calming process and solutions may vary from city to city, one thing remains constant: Planning and discussion generally take far longer than implementation. Columbus’s program, for example, includes a Traffic Calming Priority Index ranking system, neighborhood surveys, “neighborhood kickoff meetings,” “re-group meetings” and “neighborhood consensus meetings.” Referring to the untold night meetings and endless back-and-forth dialogue between city officials and residents, Tweed sums it up aptly: “No pain, no gain,” he says.
According to the American Institute of Architects Guide, New York City has a total of 2,098 bridges, excluding the Manhattan Transit Authority’s more than 70 miles of elevated track or its Park Avenue Viaduct. For the New York Department of Transportation’s Division of Bridges, keeping those vital links open and safe is a never-ending task.
As the structures age – many already are near or past the century mark – maintenance issues become correspondingly more urgent. To address those needs, the city launched the Bridge Component Rehabilitation/Replacement program in 1995, spearheaded by the city’s program director, James Cusack.
New York-based Gandhi Engineering was one of the first consultants retained by the New York Bureau of Bridges under its Component Rehab program. The firm provided inspection and design work for nine bridges in Manhattan and the Bronx.
The oldest structures, such as the 96-year-old Riverside Drive viaduct, often posed the trickiest challenges. Built in 1902, the viaduct features ornate Victorian abutments of carved granite that completely enclose and conceal some portions of the structural steel. Additionally, graceful, interlaced supporting arches are formed by an overhead framework of some 400 riveted members underneath the roadway.
To preserve the bridge, engineers changed the structural system, upgraded many components and replaced corroded rivets with high-strength bolts. (The bridge’s age and the type of steel used during that period made welding inadvisable.)
Engineers specified lightweight concrete to minimize the load on the reconstructed viaduct. For quality assurance, samples were taken before and after the concrete was pumped, and four test cylinders – two pre- and two post-pumping – were sent to an independent lab for evaluation.
Cylinder tests showed the aggregate had the specified strength, opening the way for its use on other city bridge projects. The revamped bridge was back in full service on schedule in early summer. The viaduct was the first bridge project in the city in which the contractor was authorized to pump lightweight concrete.
Three of the bridges, including the Riverside Drive viaduct and the southbound ramp overpasses of the Henry Hudson Parkway, were in the vicinity of West 96th Street. Others included a pedestrian bridge over Third Avenue at East 128th Street and another bridge carrying the southbound Henry Hudson Parkway over a pedestrian path in Inwood Hill Park.
To minimize inconvenience to the public, the rehabilitation projects were put on a fast track, allowing bridge contractor Melwood Construction, Queens Village, N.Y., to start on repairs while portions of the rehab design still were under way. The city also awarded design-build contracts to further speed up the repair projects.
“Big bridges tend to seem more glamorous and interesting to experts as well as the public,” notes structural engineer Stan Jarosz. “But the small ones are more varied and sometimes equally challenging. They are also much more numerous, and they can be just as vital to a city’s transportation system.”
In 1996, Schererville, Ind., needed to extend 77th Avenue westward about three-quarters of a mile between U.S. 41 and Patterson Street. The land’s organic soils, however, were deemed too weak to support the weight of road materials.
The municipality searched for an affordable, environmentally safe solution and decided to use expanded polystyrene (EPS) geofoam blocks. On the recommendation of its engineering firm, Chicago-based McDonough Associates, Schererville entered into a contract with Polyfoam Packers, Waukegan, Ill., to manufacture and deliver 11,500 cubic yards of the blocks to the work site.
The block manufacturer worked closely with the contractor, Rieth-Riley Construction, Gary, Ind., providing on-site coordination as well as technical and logistical support for installation of more than 120 trailer loads of the geofoam blocks. Using EPS as a lightweight fill made it possible for the contractor to build a higher road embankment and minimize the load on the weak sub-base.
The 77th Avenue project involved the use of 3,300 geofoam blocks (some as long as 16 feet), laid in a 38-foot wide road base. At the east end of the fill, the blocks measured 3 feet in depth, but, from the center to the west end, the blocks were layered 5 feet deep. The entire length of the fill was topped with 4 to 5 inches of reinforced concrete slab, then gravel and finally the asphalt road surface.
The project cost $1.6 million, including $600,000 for the blocks, according to Mike Hannemann, a vice president for the engineering firm. Work was completed in about eight months.
With a total of 37,408 miles of public roads and 6,400 bridges to maintain, the construction division of the West Virginia Department of Highways (WVDOH) administers, tracks and maintains all highway construction documentation in the state. That involves maintaining extensive files and databases of information for original estimates, contracts, change orders, traffic engineering, rights-of-way, structures and general correspondence.
During 1996, WVDOH managed projects that resulted in the resurfacing of 1,600 miles of highway, replacement or renovation of 200 bridges, installation of 360,000 feet of new guardrails and repair of 125 slide sites. New construction on federal highways and beautification and cleanup were among the department’s numerous other projects.
Several years ago, the department undertook a document imaging and workflow automation project to electronically track and manage its documentation. For the project, WVDOH purchased the MI3MS 3000 Plus Image and Information Management System from Minolta Information Systems, Mahwah, N.J.
The department’s 30-user network includes eight document scanners, a 50-platter optical disk storage jukebox and a 25-user workflow module. The approximately 100 people with access to the system now have immediate and up-to-date electronic access to the latest documentation on all of their department’s construction projects. The project has met all key objectives, including: * A substantial reduction of floor space, off-site storage facilities and personnel time devoted to file storage and retrieval. Costs associated with lost and missing files have been reduced, as have the general administrative costs, which often constituted more than 10 percent of total project cost; * Complete elimination of four large paper storage systems as well as hundreds of file cabinets and storage boxes kept at various locations; * Quicker access to documentation, including significantly improved efficiency in file search and retrieval time; * Improved staff interaction and productivity resulting from an open work environment free of clutter and file cabinets; and * Faster response time to contractors and sub-contractors as well as improved project tracking, change orders, timetables, reporting, and final performance and outcomes.
The conversion to paperless record-keeping was started in 1992, and “It’s never finished,” according to Joe Ferguson, information systems engineer with WVDOH. The new system has saved the department thousands of dollars but has not resulted in a reduction of personnel. “It’s made the work group more efficient,” Ferguson says.
Easy access to underground utilities can save public works departments money, not to mention hours of hard work. Realizing that, Indianapolis has passed an ordinance mandating the use of flowable fill in projects requiring backfill material. The city hopes to speed up street projects and prevent the dips or bumps that can form when conventional backfill is used.
Flowable fill, a blend of cement, fly ash, sand and water, is a self-leveling and self-compacting material. It has the consistency of pancake batter during placement and can support heavy loads after drying in just a few hours. It is used as backfill and structural fill for projects including abandoned underground storage tanks and vaults, wells, sewers and manholes.
The conventional way to backfill a construction area is to place a gravel and sand mix into a trench, pack it in several layers and then cover it with pavement, according to Mike McBride, director of technical services for the Indianapolis-based Indiana Ready Mixed Concrete Association. The packing of conventional material requires that it be tamped or compacted, which takes extra time and adds to the cost of the project.
Indianapolis has used flowable fill in numerous projects, including roadwork near the Arts Garden, a steel-and-glass auditorium built over an intersection and attached to a mall. When crews dug up the street, the maze of parallel and perpendicular pipes underneath the pavement would have been difficult to fill with conventional sand and gravel backfill, according to Mark Smith, the city’s assistant administrator for code compliance.
Indianapolis is one of the first cities in the country to pass an ordinance mandating use of flowable fill. “The initial costs look higher, but overall, flowable fill costs less to use,” Smith says. “It saves taxpayers money because it works the first time out.” – Peggy Caylor