Adapted from Transit-Friendly Streets: Design and Traffic Management Strategies to Support Livable Communities, published by Project for Public Spaces
Transit-friendly streets are places that "balance" street uses over having any single mode of transportation dominate. In many cases, this means altering a street to make transit use more efficient and convenient, and less so for automobiles - while still accommodating them. When these alterations are done right, a kind of equilibrium is achieved among transit, cars, bicycles, and pedestrians. Transit-friendly streets accomplish the following four goals:
Because streets have many different patterns of use, there is no single way to achieve an optimum balance. Therefore, formulaic solutions such as transit malls (described below) sometimes fail. However, we have found that this balance can be achieved more effectively when the public participates in the planning process.
This section offers general strategies for creating transit-friendly streets that focus balancing the needs of people in transit vehicles and automobiles, bicyclists, and pedestrians. Of course, not all the strategies apply to every situation, which is why an initial assessment of the functioning of a street is so important: understanding the nature of the problems on a street is the first step toward developing effective solutions to those problems.
A principal issue for any commercial street is the space allocation for pedestrians and vehicles - which is complicated by the diverse types of vehicles on most commercial streets: transit vehicles, private cars, delivery trucks, bicycles, etc.. To create livable, walkable communities, pedestrian space should not simply consist of what is left over after all vehicle uses are maximized. Rather, developing a strong pedestrian orientation for a street can help encourage decision-making about transit and vehicle use, which can benefit the long-term livability of a neighborhood. After all, every transit rider is a pedestrian at some point during his or her trip!
City sidewalks are not just pedestrian thoroughfares; they function as social places where people gather to talk, meet friends, or watch other people. Ideally, a sidewalk should be wide enough to accommodate pedestrian movement as well as seating, trees, bus shelters, and other appropriate amenities that support social activities.
Determining the proper width of a pedestrian space is more complex than it initially appears. Sidewalks are divided into imaginary lanes: the two or three feet adjacent to store windows acts as a "viewing space" for window shoppers; while at the curb, people generally keep a 1.5-foot distance between themselves and trees, signposts, traffic signs, etc., thus creating a second lane. In between is the "walking space," with a minimum desirable width of eight feet, or the amount of space needed for two pairs of pedestrians to pass each other comfortably. (There is no such rule of thumb for the maximum width of a walking space, although too much space is just as undesirable as too little - it makes a place seem "empty" if people are distributed over too large an area).
Street space can be made available for pedestrian use in a number of ways, such as eliminating on-street parking; rerouting or restricting traffic to certain hours or certain lanes; calming traffic speeds to encourage through traffic to go elsewhere; and giving priority access to buses. To balance the needs of pedestrians and vehicles, however, it is necessary first to understand how vehicles, whether they be transit or other types, use a street for through movement, passenger pickup and discharge, parking, and deliveries. Ultimately, the kinds of changes that can be made to a street are limited by the width of the street and by other physical constraints, including local laws and jurisdictional ordinances.
Sidewalk "Nubs" or "Neckdowns"
Even if an entire street cannot be modified, it still is possible to make improvements by widening sidewalks at congested locations or intersections. Variously termed neckdowns, nubs, bulb-outs, bus bulbs, bump-outs, and curb extensions (depending on the region), these extensions are an inexpensive way to reconfigure a street to accommodate pedestrian, vehicular, and transit uses.
Bus nubs are sidewalk extensions that include a bus stop, and extend through the parking lane up to the travel lane. This enables buses to stop in the travel lane to drop off and pick up passengers, eliminating buses weaving in and out of traffic and reducing conflicts with automobiles. It also speeds passenger boarding and reduces dwell times, making transit service more efficient (unlike a bus "lay-by" or "bus bay," where the average delay of a bus pulling in and out is 10 to 20 seconds, which can double the loading time). Nubs also provide additional space for patron amenities, make boarding and alighting more comfortable, and can reduce pedestrian crossing distances. Unlike transit priority lanes, bus nubs do not require special traffic enforcement.
Nubs also improve the comfort of waiting passengers, reduce the use of lay-bys for illegal parking, and usually cost less to construct than bus lay-bys (about $3000 to $5000, versus $20,000 for a lay-by). However, bus nubs can be expensive if, for example, street drainage systems also need to be reconfigured. One French manufacturer developed a steel-fabricated bus nub with a built-in shelter that can be installed over an existing street, allowing runoff to filter underneath. (This system can be used to test a bus nub before a permanent installation is made.)
Based on their study of nubs in San Francisco, the Texas Transportation Institute reported that nubs also benefit pedestrians and bus riders because they
The ADA requires specific sizes and dimensions for boarding areas at bus stops. Curb extensions help create large enough bus stop and landing areas to accommodate wheelchairs and other passenger-related amenities, as well as retail, displays, and outdoor cafes.
The enhancement of transit-friendly streets does not end at the curb but rather, should also include the design of the sidewalk space. All too often, transit stops lack amenities for riders, in some cases because of insufficient space but in other cases because of lack of resources. Two concurrent TCRP studies-"The Role of Amenities and Vehicle Characteristics in Increasing Ridership" and TCRP Report 19, "Guidelines for the Location and Design of Bus Stops"-explore opportunities for amenities to affect passenger experience and transit choice and give many practical suggestions for their implementation.
From a transit perspective, there are two ways to provide amenities. Most common are bus and light-rail stops spaced along a street. However, consolidation of bus stops into a transfer center allows for a concentration of passenger amenities in a single location, much like commuter rail or subway stations.
When transit amenities are located on sidewalks, they are usually part of a range of "street furniture," so named because they make a street more pleasant and comfortable to use. In addition to bus shelters, amenities can include seating (on benches or planter ledges), trees, telephones, light fixtures, trash receptacles, and information kiosks; clocks, fountains, sculpture, drinking fountains, banners, and flags are sometimes provided as well. The sale of food and other items can also help stimulate activity on the street, as part of store displays, either in movable pushcarts or in permanent stands. Therefore, food vending can be considered an amenity as well.
Although amenities can make a street more comfortable and active, their mere presence will not ensure that they will be well used. Careful attention to design and location is important. Bus shelters (without walls or with short canopies) often afford little protection from the sun, rain, and wind and provide few places for people to sit or lean while waiting. Seating may go unused if it is situated too far from areas of activity or if it is facing the wrong way. When amenities are located on a bus bulb but are poorly sited, blocking pathways to bus doors, or obstructing views to approaching buses, the nub will not function efficiently for passengers or pedestrians. In addition, if not properly arranged, street furniture and transit shelter amenities can restrict access by wheelchairs (16).
A transit-priority (or transit-only) lane is one of most common strategies used to improve transit efficiency on a commercial street, either as part of larger projects (such as a transit mall) or separately. Although transit priority lanes seem like a straightforward strategy, they may not always work as intended.
Enforcement of priority lanes is difficult, as it is often impossible to keep private vehicles from using reserved bus lanes, especially when vehicles making right turns must occupy these lanes, sometimes for two blocks or more. On Main Street in Rochester, New York, the city created curb lanes for buses only (except for vehicles making right turns). In reality, however, the lane is frequently obstructed by cars picking up or dropping off passengers or by vehicles making deliveries (which are supposed to be made from side streets). The bus lane is not well marked, and there are no diamond markings on the pavement. Such markings, including 8-inch solid lane markings between the transit lanes and regular traffic lanes, are essential for effective priority lanes.
In San Francisco, where there are over 10 miles of transit priority lanes, experience has shown that these lanes work most effectively when rigorously enforced. However, competing demands for traffic control officers make such enforcement difficult. On O'Farrell Street in downtown San Francisco, a different approach was tried: left-sided transit lanes were created, with a boarding island for bus patrons. The combined strategy of left-sided lanes and regular enforcement succeeded in making the transit priority lanes work more effectively.
To address the problem of infringement of transit priority lanes in highly trafficked areas, cities may establish a "contraflow" system with buses in a single lane moving in one direction and cars in the remaining lanes traveling in the opposite direction. This is the case with a new transit priority lane under construction on Orange Avenue in downtown Orlando, Florida. This approach, however, can cause safety problems for pedestrians who may not be expecting a vehicle coming from the opposite direction.
It is not unusual for bus lanes to be installed as a separate feature. However, the impact is usually limited to improving operational efficiency of the buses and does not include the effect on the livability of a street. For example, in New York City, two lanes on Madison Avenue were converted to bus-only lanes during morning and evening rush hours. The level and intensity of bus usage, while operationally more efficient, creates an unpleasant pedestrian environment, especially during rush hours. A similar situation occurs on Spring Street in downtown Los Angeles.
As with buses, surface trams and light rail must meet passenger needs with regard to safe access to transit stops while assuring efficient train operation. A TCRP study performed by Korve Engineering entitled "Integration of Light Rail Transit into City Streets" (TCRP Report 17), investigated safety problems experienced in light-rail projects. Design solutions suggested by that report seek to "respect the existing urban environment (unless a specific urban design change is desired)" and "comply with motorist, pedestrian and LRV (light rail vehicle) operator expectancy" (17). To reduce confusion for both pedestrians and motorists, the goal should be to not drastically alter an urban environment when light rail is introduced. Moreover, it is generally preferable to provide a dedicated right-of-way for LRVs by using pavement bars, rumble strips, cobblestone pavers, and mountable curbs instead of simply striping the pavement to separate light-rail operations from cars in the middle of a two-way street.
However, the degree of transit priority may vary depending on the situation. In Sacramento, California, light rail operates on different streets in different ways, depending on the type and function of the street. For example, in outlying residential areas, LRVs travel in their own right-of-way along a grassy corridor adjacent to major arterials. As they approach downtown, the right-of-way shifts to the street but is separate from automobiles. On the transit mall and in the central business district, however, light rail shares lanes with automobiles and buses.
Traffic-calming measures that reduce the speed of vehicles are commonplace throughout Europe, and there is increasing interest in the United States. From a transit perspective, traffic calming by itself can reduce transit efficiency and make it less convenient. As a result, a 1991 survey of bus operators in Great Britain showed that "Generally speaking, the measures that are most acceptable are those that cause no or little delay and allow a smooth and continuous movement of buses." Preferred traffic-calming measures for streets with transit include methods that created "pinch points" instead of changes in street elevation (although raised crosswalks are acceptable); road narrowing by road markings; mini-roundabouts; bus berths or nubs; and changed road surfaces with materials such as pavers (it is important to structure pavers for the weight of a bus).
Many traffic-calming strategies exist. Deployment of specific strategies is determined by the number of vehicles per day and, most significantly, according to the most desirable travel speed for vehicles on a particular roadway. Staggerings, gates, and prewarnings are recommended for roadways with more than 3000 vehicles per day and with speeds greater than 35 mph - conditions found in many American cities and suburban areas. In a more densely settled downtown core, along local roads where vehicles travel more slowly but that still serve over 3000 vehicles per day, additional measures such as raised areas and lane narrowings are also recommended.
Although bus nubs are increasingly being used in the United States, it should be noted that, by themselves, they are ineffective as a traffic-calming measure because they are usually spaced far apart. In fact, research in San Francisco showed that delays for motorists caused by nubs are small or nonexistent, because many buses fail to pull fully out of the traffic lane at a stop. In Portland, Oregon, however, traffic engineers emphasize that installing nubs at bus stops makes the street safer because cars are less likely to try to pull around and pass a bus that is only partially in a bus stop lay-by area.
Finally, another common strategy used in Europe, based on years of experience with traffic calming, is to completely segregate transit from a traffic-calmed area - as long as walking distances are less than 300 meters from the traffic-calmed places, according to one study from England. "Rerouting buses from streets chosen for traffic calming on to other streets may be an option and is very often now chosen by bus operators themselves," the study reported. However, official government policy is that "in shopping areas, access to buses should be at least as convenient as to car parks."
Signalization changes and other design features at intersections can also have a positive impact on transit efficiency. For mixed traffic and transit priority lanes alike, these strategies can help provide additional priority for transit vehicles. On Upper Market Street in San Francisco, it simply was not possible, for example, to create transit-exclusive lanes without creating untenable traffic congestion. The solution was to mix streetcars and automobiles but to time signals to minimize traffic delays caused by boarding and discharging of passengers. This strategy is working well, as traffic flows evenly and the streetcars cause no delays to other vehicles. However, as with other strategies, it is important to weigh other considerations at intersections, such as the effect of their design on pedestrian movement.
The geometry of intersections and the timing of the traffic signals are often designed for the needs of vehicles rather than pedestrians. For example, traffic engineers often prefer wide curb radii that make it easier for vehicles to turn. However, the larger the radius, the more inconvenient and dangerous it is for pedestrians to cross the intersection, because there are cars turning in front of and behind them. Greater ease of turning leads to speedier vehicle movement and less time for pedestrians to establish right-of-way when crossing the street.
Narrowing the street width, by widening sidewalks along the full length of a street or just at intersections, can facilitate pedestrian crossing. Another advantage of bus nubs located at intersections is that they too create shorter pedestrian crossings and safe waiting places, often enhanced by amenities, while making it unnecessary to alter traffic lanes.
Traffic management strategies, such as signalization changes, restricted turning movements, and reduced traffic speeds, can clearly reinforce these design changes. As noted in AASHTO's A Policy on Geometric Design of Highway and Streets, "Traffic control devices on arterial streets are usually installed with the intent of favoring automobile traffic with only secondary consideration to transit vehicles... Where local service is provided by buses, however, with frequent stops to pick up and discharge passengers, a signal system that provides for good progressive movement of privately operated vehicles may actually result in reverse progression for buses. The resulting slow travel speed for buses tends to discourage patronage, further adding to the already heavy volume of automobile traffic."
Signal preemption is a system installed to hold a green light for transit vehicles or to change the light to green after a minimal period so that transit vehicles need not stop at an intersection. A variety of technologies can be used, ranging from contacts on light-rail overhead wires to systems using radiowaves or soundwaves.
In San Francisco, 16 intersections were outfitted with this technology in 1988. For trolley coaches and light-rail vehicles, preemption is triggered by contacts on overhead wires. An analysis of the impact showed a reduction in transit delay of 6 to 10 percent. However, newer systems have been less reliable technically and seem to require a high level of maintenance, including weekly inspection. Installation costs, averaging $30,000 per intersection, are not insignificant. The city is investigating other options to reduce initial and ongoing maintenance costs and to increase reliability.
A simpler system was used on Upper Market Street in San Francisco. Here, the regular signal is timed to the speed of the streetcar, which shares a travel lane with cars. As the streetcar approaches the stop, the light turns red, allowing passengers to get on or off the vehicle. By the time the light changes to green, passengers are seated and the streetcar can proceed, without further delays to motorists.
More recently, Pace, the suburban bus provider in Chicago, has been experimenting with a system in which buses with a special "transponder" (costing about $10,000 per bus) send a signal to coils buried in the pavement about 250 ft from an intersection. These coils trigger lights to stay green a little longer or to change from red a little faster. As a result, trips along an experimental corridor have been reduced by 2 to 3 minutes. Although the system has not yet been evaluated. Pace is generally pleased with the results to date and intends to consider adding technology that will affect the signal only when a bus is behind schedule.
With this signalization system, buses and trams are given a head start at intersections; that is, buses get a green light before automobiles do. Because transit vehicles get a jump on automobiles queuing at a red light, they merge more easily back into traffic. In Europe, where this system is common, priority green not only has been effective in speeding transit but also has had a negligible effect on private car traffic. In addition, journey times for trams and buses are now shorter and the speeding up of service (by about 5 km per hour, or 20 to 25 percent) often means that one less vehicle has to be deployed, which can save the transit operator money.
Transit priority signals can be activated by the vehicle or the transit driver. If the vehicle is traveling in a dedicated lane or right-of-way, a detector that triggers the traffic signal to change can be imbedded in the pavement. If the transit vehicle is moving in mixed traffic, the driver can trigger the traffic signal from the vehicle. According to the Ontario Ministry of Transportation, this method is most effective when it is used at intersections where transit vehicles face routine delays because of heavy volumes of automobile traffic or where transit vehicles need to make left turns against steadily oncoming traffic.
Both the early green and queue-jump transit priority strategies (the latter is described below) were tested at four intersections in Portland in the early 1990s. In general, bus travel times decreased in the peak period in the peak direction. Also, vehicle delay did not change significantly, and the delay for bus passengers decreased 12.3 percent with bus priority.
Another strategy to provide transit priority at intersections is to narrow streets at transit stops to prevent automobiles from passing buses and to reduce the danger to pedestrians crossing the street to the bus stop. This method, called "queue jump," is most easily accomplished by transforming a right-turn lane with simple signage (such as "right-turn only except buses") and then providing a small bay on the far side of the intersection for buses to reenter the flow of traffic. In Devon, England, for example, this is common practice and is very successful.
Many transit planners believe that this technique is most appropriate for use on roadways with heavy volumes of automobile traffic. The Phoenix and Orange County manuals cited by the Texas Transportation Institute (in TCRP Report 19, "Guidelines for the Location and Design of Bus Stops") recommend queue-jump lanes at arterial street intersections in the following situations:
The report also suggests that when right-turn volumes exceed 400 vehicles per hour, an exclusive near-side bus lane be added to the near-side right-turn lane as well.
The opportunities to create transit-friendly streets clearly will be enhanced by emerging technologies that give greater control for all modes of vehicle traffic. Automatic vehicle locator systems, for example, increasingly are used to monitor buses in service with satellite connections to a central dispatch. When buses are delayed, the dispatch unit receives information from a transmitter attached to the bus and additional buses can be deployed. Similarly, information received from the buses then can be relayed to passengers waiting at the bus stops. Using these technologies in combination with other design and traffic management strategies will facilitate the development of transit-friendly streets in the future.