Bus-on-shoulder operations, also known internationally as "bus bypass shoulder" (BBS) operations, are a low-cost strategy allowing buses to travel at or near free-flow speeds through congested arterial and freeway routes. BBS describes the routing of a bus onto the shoulder of a road, usually a highway, in lieu of the standard general-purpose lanes. BBS is a policy-based alternative to constructing dedicated rights-of-way or restricting lane use to high-occupancy vehicles (HOV). The primary goal is to prioritize the reliable performance of public transit over capacity for single-occupant vehicles (SOV). Bus-on-shoulder is typically used only where roadway congestion is severe enough that traveling on the shoulder improves on-time reliability and even decreases overall trip time.
Currently, bus-on-shoulder programs have been implemented in 13 metropolitan areas in the United States, as well as in metropolitan areas in Canada, New Zealand, the United Kingdom, and Ireland<ref>Zuehlke, J., Kaba, F., McElduff, K., Ho, L. S., & Machemehl, R. PEAK PERIOD BUS USE OF FREEWAY SHOULDERS. 2015</ref>. In the United States one of the most extensive networks of bus-only shoulders is found in Minnesota<ref>Minnesota Department of Transportation. Bus-Only Shoulders - A Transit Advantage</ref>.
In the United States, bus-on-shoulder programs typically restrict bus use of the shoulder to periods when the free-flow speed drops below a particular threshold (e.g. 35 miles per hour in the Twin Cities and Columbus, 25 miles per hour in Miami), and prevent buses from traveling more than 10 mph (San Diego) to 15 mph (Twin Cities) faster than the general-purpose lanes — up to the threshold speed of 35 mph<ref>Martin, P. C. Bus Use of Shoulders (Vol. 64). Transportation Research Board. 2006</ref>, <ref>Florida Department of Transportation. Implementing Bus on Shoulder in Florida. 2016</ref>— for safety purposes. The speed-based restrictions do not seem to apply in Ottawa, Canada where busses can use the lanes 24 hours a day<ref>National Academies of Sciences, Engineering, and Medicine. A Guide for Implementing Bus on Shoulder (BOS) Systems. 2012</ref>. Ten feet seems to be the minimum width of shoulder accepted by agencies for use in bus-on-shoulder programs, with a 12-foot width recommended in Minnesota<ref>Douma, Frank. “Bus-Only Shoulders in the Twin Cities.” Minnesota case study. 2007</ref>, <ref>Florida Department of Transportation. 2016</ref>. In San Diego, shoulders were widened to 11 feet by narrowing the inside shoulder <ref>Zuehlke, et. al. 2015</ref>. The desired pavement thickness for a shoulder in the Twin Cities is 7 inches (capable of withstanding the bus’s weight)<ref>Douma, Frank. “Bus-Only Shoulders in the Twin Cities.” Minnesota case study. 2007</ref>. The design of catch basins and rumble strips in the shoulders have been altered in the Twin Cities to accommodate a smoother bus ride<ref>Douma, Frank. 2007</ref>.
Despite the modest speed improvements they enable, bus-on-shoulder programs have improved on-time performance in the Twin Cities, San Diego and Miami<ref>Zuehlke, et. al. 2015</ref>. Riders, in particular, seem to perceive a significant time savings from the lanes (possibly a result of the effect of the bus moving quickly past congested lanes). Passengers in Ohio, San Diego, and the Twin Cities have given positive feedback on the lanes<ref>Zuehlke, et. al. 2015</ref>. By making use of existing freeway infrastructure, bus-on-shoulder lanes have cost as little as $1,500 to $100,000 per lane-mile to implement in the Twin Cities, a figure considerably less than adding a new lane (with an average cost of $2 million to $10 million per lane mile<ref>Texas A and M Mobility Institute. Adding New Lanes or Roads.</ref>) or implementing mixed-lane bus rapid transit systems (which cost $1 - $7 million per mile on average<ref>Transportation Research Board. TCRP Report 118: Bus Rapid Transit Practitioner’s Guide. 2007</ref>), with arguably greater effects on performance. In addition, bus-on-shoulder lanes in the Twin Cities might have improved performance for bus services that don’t use the freeway by permitting the out-of-service buses to deadhead quickly<ref>Metaxatos, P., & Thakuriah, P. Planning for Bus-on-Shoulders Operations in Northeastern Illinois: A Survey of Stakeholders. 2009</ref>.
Another advantage of this strategy is improved access on and off a highway, which can speed up passenger stops, especially for express-style service.
If local, regional, or state policy allow, BBS can be very quick to implement. Because there are few to no infrastructure costs, implementation could be as simple as rescheduling and retraining. It may be a challenge to motivate policy makers to allow BBS given its limited use in the United States. Some areas have allowed limited demonstration projects, an example of which is described below.
A successful bus-on-shoulder operation requires control of bus access to the shoulder when the flow of traffic falls below the speed threshold<ref>Metaxatos & Thakuriah. 2009</ref>. Control of entry is needed both to signal to busses that it is okay to use the lane and to prevent cars from following busses into the lane.<ref>Eichler, M. D. Bus Lanes with Intermittent Priority: Assessment and Design . 2005</ref> Moreover, access should be limited, as in the Twin Cities, to licensed transit (or intercity bus) operators, to maximize the benefits to public transport<ref>Douma 2007</ref>. Dynamic, electronic road signs that change their display to indicate when buses are allowed in the lanes, may help solve the problem<ref>Florida Department of Transportation. 2016</ref>.
Operating any vehicle on the shoulder of a high-speed facility significantly increases risks. As MNDOT notes, the exception is limited to buses, which are driven by highly trained professionals. Shoulders are generally reserved for emergency vehicle access and to provide safe haven for disabled vehicles. While a bus operator should be able to see stopped vehicles well enough in advance to merge into the next lane, circumstances can change quickly leaving the operator fewer options for escape. The bus-on-shoulder program in Atlanta has addressed this conflict by creating additional pull-outs on the right side of the shoulder for emergency or enforcement vehicles<ref>Florida Department of Transportation. 2016</ref>.
Visibility around access ramps can also be a challenge. Older facilities may have very narrow exits or on-ramps making a challenge both for the bus traveling at high speed and other vehicles entering the highway.
However, the bus-on-shoulder program in the Twin Cities, the longest-running program, has had a good safety record, with only 20 accidents — none involving fatalities — occurring in the first decade of the lanes’ implementation<ref>Douma 2007</ref>. Conflicts with merging traffic on the right shoulder can be averted through ramp metering technology (as done in Vancouver<ref>BC Transit. Infrastructure Design Guidelines. January 2010.</ref>) or by permitting use of the right shoulder only where the bus makes frequent exits and/or on-or-off ramps occur infrequently<ref>Metaxatos & Thakuriah. 2009</ref>. The only bus-on-shoulder program in the US to encounter a major accident, along a segment of Route 9 in Middlesex County, New Jersey, lacked special speed restrictions (busses could travel at the normal maximum speed), suggesting the importance of the 15 mile per hour limit on the speed differential (and a lower maximum speed limit) for safe operation<ref>Florida Department of Transportation. 2016</ref>.
In cold climates, the shoulder may be essential for snow storage if it cannot be cleared beyond the paved surface, diminishing the practicality of the bus-on-shoulder service.
More generally, intergovernmental cooperation is necessary for systems’ implementation in the United States given the separation of responsibility for road planning and transit operation<ref>Agrawal, A. W., Goldman, T., & Hannaford, N. Shared-use bus priority lanes on city streets: approaches to access and enforcement. Journal of Public Transportation. 2013</ref>. In previous instances, implementation required collaboration, at a minimum, between a metropolitan transit agency, the agency in charge of the road (often a State DOT), and an enforcement agency (e.g. in Minnesota<ref>Douma 2007</ref>, Virginia<ref>Martin, Peter C. "Bus Use of Shoulders." Transportation Research Board. 2006.</ref>, Atlanta<ref>National Academies of Sciences, Engineering, and Medicine. 2012</ref>). In San Diego, the collaboration has occurred between SANDAG (the Metropolitan Planning Organization) and Caltrans<ref>National Academies of Sciences, Engineering, and Medicine. 2012</ref>. In Minnesota, a collaborative partnership titled “Team Transit,” spearheaded by the Minnesota Department of Transportation and the regional transit authority, Metro Transit, and including city governments and the state highway patrol, has led the regional bus on shoulder project. The Florida Department of Transportation’s Statewide Guidance for Bus on Shoulder Implementation recommends that transit agencies (who are knowledgeable about local service patterns) initiate bus on shoulder proposals and that the State Department of Transportation review (and approve) these proposals<ref>Florida Department of Transportation. 2016</ref>. However, the document assumes a piecemeal implementation process, by which each proposal results in the formation of a separate task force. A statewide bus-on-shoulder program should involve input from both local transit agencies and the State Department of Transportation, which may be best informed to determine alignments’ safety and feasibility, and requires a large-scale planning framework spearheaded the state agency, but that draws on input from all stakeholders.
Applications in California
A November 2006 newsletter produced by the San Diego Association of Governments (SANDAG) noted that the San Diego Metropolitan Transportation System (SDMTS) Route 960 had been operating a 10-month trial of bus-on-shoulder service. Benefits of the project were 99% on-time performance, high customer satisfaction, and measurable time-savings for commuters. No accidents had been observed in the BBS portion of the service at the time<ref>SANDAG. the rEgion Newsletter. "Buses on shoulders - a smooth ride" November 2006</ref>. At the time of this writing, that project had concluded and was discontinued due to new construction on the highway. According to information on the SANDAG website, no other BBS service is operating currently, but SANDAG and SDMTS are working to develop a new BBS service elsewhere.
Outside of urban areas, California has several freeway corridors with at least 6 long-distance bus services a day that are subject to regular congestion. These include Interstate 15 from the Cajon Pass to the Nevada State Boundary and Interstate 5 from Irvine to San Diego. Designating shoulder use for bus services on these routes can help reduce travel time and increase ridership on intercity bus service from Los Angeles to Las Vegas<ref>Wanderu.com search. September 6, 2017</ref> and from Los Angeles to San Diego<ref>Wanderu.com search. September 6, 2017</ref>. A precedent for intercity bus use of highway shoulders can be found in Ireland, where the long-haul bus operator, Bus Eireann, can use shoulders on highways approaching Dublin<ref>Hogan, Tracey. "Buses can use hard shoulder to beat 20 m delays." Independent.Ie. December 29, 2004.</ref>. Given the needed for unimpeded travel over a long-distance, use of the left shoulders would be preferable on these routes.