Though traditionally viewed as a “resort-based” transport system, the aerial cable-propelled gondola is gaining traction as a viable commuting option in busy urban settings.
San Diego is one of the first U.S. cities giving serious consideration to this emerging transit option, and WSP USA provided the planning and conceptual engineering services for a feasibility study that could pave the way for the creation of the Bay-to-Balboa Skyway.
The study was performed for the San Diego Association of Governments (SANDAG) through the firm’s collaboration with Dopplemayr USA, a company that has already implemented similar technology in 30 cities around the world.
The result was a detailed study completed in June 2015 that visualized a two-mile skyway along the Sixth Avenue corridor, from the Gaslamp Quarter in downtown San Diego to Balboa Park. Rex Plummer was the principal-in-charge, Jeff Howard was the project manager, and Chris Wahl was the deputy project manager.
The study examined potential alignment options, station locations, potential environmental and community considerations, ridership, costs and funding opportunities. The final report discusses the system profile, including speed, distance, dimensions, ridership capacity, tower and station locations and design.
Conclusion? An aerial skyway is not only feasible, but the system could be successfully integrated into San Diego's existing infrastructure, and constructed and operated at a cost far below other public transportation options in that area.
“The use of eight-passenger cabins would be the first in the U.S. in an urban environment,” Wahl said. “Currently, eight-passenger systems are used only at mountain resorts.”
An aerial cable-propelled transit system was not even on the radar when SANDAG started looking for a firm to conduct an alternative public transportation study as part of its 2050 Regional Transportation Plan.
That all changed after WSP suggested the concept of exploring a “skyway” similar to La Paz, Bolivia, which has three lines in operation and is expected to expand the system to 10 lines and nearly 13 additional miles of service.
The skyway feasibility study was proposed as a stand-alone assessment by County Supervisor Ron Roberts, who had seen similar systems in other parts of the world, and thought it could flourish in San Diego. Roberts secured a Neighborhood Investment Program grant that made the study possible.
“The skyway study is a perfect example of WSP bringing to our client an innovative idea that opened the door for SANDAG to study urban aerial cableway as a viable mode in this and other corridors,” said Rex Plummer, area manager for the San Diego office. “Urban aerial cableway is an alternative transportation mode that has been successfully integrated into transit networks in various foreign cities around the globe.”
One of its potential advantages is its ability to avoid obstacles in the built or natural environment, such as railway lines, freeways, water bodies; or significant changes in topography, such as canyon and valleys.
“A skyway avoids the need to build the highly expensive infrastructure typically required for light rail transit or major dedicated rapid bus facilities,” Jeff Howard said. “Our study follows the existing street right-of-way and is essentially barrier-free because the cabin rises above the street and the towers supporting the system have a small footprint on the ground.”
Although the client did have some reservations regarding the application at the onset, the potential benefits of an aerial gondola system soon began to address many of the client's concerns.
“When we began the study, many considered the Skyway more of an ‘amusement ride’ than a viable mode of transit,” said Chris Wahl, deputy project manager. “But the more the plan evolved, those skeptics started to see that the technology can have some real utility in the urban environment.”
“The skyway has the potential to be the next generation of mobility, once again placing San Diego at the forefront of transit and mobility innovation,” Plummer said.
The feasibility study – which began in January 2015 and was completed in June – estimates that the skyway would cost $65-to-75 million to construct, whereas a light rail system covering the same area could cost $300-to-400 million. As an all-electric system, it would require less energy to operate than other options, which would contribute to lower overall operating costs and potential reduction in greenhouse gas emissions.
In addition, a skyway system allows for more direct routings, often providing the fastest route from point-to-point in a safe, elevated environment.
“Eight-passenger cabins could arrive as frequently as every 12 seconds, traveling 14 miles per hour,” Wahl said. “They are clean, quiet, and energy-efficient.”
The system could potentially carry 2,400 passengers per direction, per hour – comparable with high-capacity bus service – and could serve an estimated one million riders annually. The Skyway would bypass all traffic congestion, and serve as an environmentally friendly alternative to ground transportation.
“It is anticipated that the travel time from end-to-end of the two-mile corridor would be approximately 12 minutes, and feature four station locations where passengers could access the system. Assessment of the potential market for ridership indicated that it would serve a mix of daily commuters and tourists. We would also expect to see an additional ridership boost due to the “novelty” nature of the system,” Wahl added.
The study identified several regulatory requirements, environmental issues and other concerns that would need to be addressed in future studies before a Skyway could be created, including visual impacts, impacts to historic districts and landmarks, and development regulations related to its proximity to San Diego International Airport.
“The height of system structures would need to be carefully evaluated in order to ensure that they do not encroach into the approach/departure path at San Diego International Airport,” Wahl said. “This is a somewhat unique challenge that we do not normally encounter when planning for transportation projects.”
The system is always in motion and cabins move about 1,200 feet per minute in between stations, slowing to a speed of 60 feet per minute while in stations. “This reduced speed allows for easy boarding and alighting to and from the cabins,” Wahl added.
Although there is presently no timetable for a formal design and construction of the Skyway in San Diego, based on the favorable results of the initial feasibility study, SANDAG is investigating the feasibility of the skyway concept for other corridors.
WSP was selected to lead one of these additional feasibility studies, and the skyway concept has been incorporated into SANDAG’s long-range transportation plan as a potential transportation solution at locations where space and terrain constraints warrant creative solutions.
“The idea of a cableway as an urban transit mode has the potential to be both a bold and creative solution for the region’s future mobility,” Howard said. “From our study, SANDAG is now able to put the aerial cableway in the toolbox as an option for future transit studies.”
The Skyway could also provide an opportunity to enhance the urban streetscape at tower locations through the creation of “parklets,” or small spaces serving as an extension of a sidewalk allowing for amenities or green space, particularly near restaurants or retail services. Parklets could be constructed in a manner that avoids reducing the number of travel lanes on Sixth Avenue.
“We believe this technology could be used in cities across the United States,” Wahl added. “In fact, several other cities are currently evaluating, or planning to evaluate, the utility of the technology as a mode of public transportation.
“The technology provides a myriad of benefits and is something that we believe can be successfully implemented across the country,” he added. “To be involved at this early stage is truly exciting, and we look forward to seeing how things develop over time.”