The Evolution of Streetcar Technology

While streetcars may seem like an old-fashioned or nostalgic mode of transportation, today’s streetcar is far from your grandmother’s trolley. The modern streetcar has evolved in major ways in response to shifts in community needs as well as technological advances.

The way streetcars are powered today, how they are designed to fit into the urban environment, and how they address the needs of modern cities have all made the streetcar a much more attractive option for transit agencies worldwide.

Off-Wire Capabilities

The most visible — or perhaps invisible — streetcar technological advances in the last decade have been in the areas of power supply and power storage, particularly the ability for trains to run without an overhead catenary system (OCS) for all or part of their route. Off-wire flexibility can be desirable for a variety of reasons, including aesthetics (the visual impact of the wire), impaired clearance (such as under bridges), utility conflicts, or challenging environments (like an extended river crossing).

The first section of catenary-free streetcar track debuted in Bourdeaux, France, in 2003 and was prompted by a desire to avoid the visual impacts of an overhead wire through an important historic district. A decade-and-a-half later, more than 20 systems worldwide run off-wire segments with several more in planning/construction. Five of these systems run off-wire for their entire routes, including in Dubai; Rio de Janeiro; Zhuhai and Guangzhou, China; and Kaohsiung, Taiwan. In the U.S., Dallas, Seattle, and Detroit have introduced off-wire segments to their streetcar systems, and additional U.S. systems have participated in testing of development prototypes.

New Options for Power Supply and Storage

The two primary options for off-wire operation are ground-level power supply and on-board energy storage systems. On-board power generation is a third option, but has received significantly less research than the other two modalities, although this may change with increased interest in hydrogen fuel cells. A small number of diesel hybrid systems area also in operation.

Ground-level power supply can be a contact or contactless system. A contact ground-level power supply essentially employs an embedded "third rail," as is typically used in metro or subway systems and was used on some early 20th century streetcar systems with limited success. Today, much-improved versions of this technology offer advantages in environments that have heavy loads from heating or cooling for passenger comfort or need to traverse steep hills — all of which can quickly drain a stored power system. The performance of such systems, however, is still questionable in cold environments with heavy use of plows and road salt.

A contactless ground-level power supply uses induction coils to power the streetcar. Typically, this power transfer takes place only when the streetcar is directly above the coils. The range of such a system is extended by combining it with on-board power storage, so that the coils do not need to be present along the entire length of the system.

On-board energy storage offers an alternative or complement to ground-level power  supply. Storage mechanisms include batteries, capacitors, flywheels, and in some cases, reclaiming kinetic energy from braking to increase system efficiency. A system that runs off-wire for a limited segment can often recharge on-board power from the OCS as it runs on a wired segment. Longer spans of off-wire operation may require a "recharging station" approach, which can be attained by sufficient dwell time at a stop. For example, the streetcar in Guangzhou, China, requires only 20 seconds of contact at the station to recharge its roof-mounted supercapacitors, recharging in the time it takes passengers to board and alight.

Increased Capacity

Modern streetcars offer significantly greater capacity than older generations of streetcars. Although streetcars typically are not designed to be coupled into multi-car consists as with light rail transit (LRT), manufacturers offer streetcars in lengths ranging from 65 to 145 feet, accommodating between 100 and 300 passengers. Streetcar widths can also vary, which can help meet both capacity and lane restriction needs. Among the wider options, 2.65 meter (roughly 8.7 feet) trains match standard LRT widths used in the U.S. and are often considered if there is any potential for streetcar and LRT to share stations or for a streetcar route to convert to LRT in the future.

Easier Boarding

Modern streetcars typically offer either "fully level" or "near-level" boarding. Fully level boarding has a set floor height of 14 inches, and requires an active suspension for load leveling. This type of boarding is often the most user-friendly option for passengers, but can be more difficult to transition into existing sidewalk, particularly in constrained sections with short distances between curb and building. Fully level stops also pose challenges for sharing stops with buses, which have a lower boarding height.

Some cities, such as Los Angeles, have chosen to address this bus/streetcar issue by creating hybrid stops with fully level, ADA-compliant loading at the two front or two rear doors of the streetcar, while the other two doors require passengers to step up into the streetcar. Buses can then pull to the non-ADA (lower) portion of the stop to open doors, which may be blocked at the higher part of the stop, and board.

Near-level boarding, on the other hand, requires a bridge plate to create a small ramp between adjacent sidewalk and streetcar, which can increase dwell time and decrease efficiency. Without the need for a tight fit between streetcar and curb, however, bridge plates make it possible to build stops on a curve and often offer an easier transition to existing sidewalk grades. Near-level boarding also permits lower stop heights and can make shared bus operations more feasible.

Cyclist Interaction

Modern streetcars systems have also evolved to pay special attention to interactions with people who are not even using them, specifically cyclists. The most dangerous interaction is often not conflict between cyclists and trains — although awareness training for both is necessary — but between cyclists and the tracks. Embedded track poses two primary risks: tires getting caught in the flange between rail and roadway, and tires slipping on rails, particularly when wet.

The preferred mitigation for these issues is to design modal intersections so that bicycles can cross the track as close to perpendicular as possible. While slight angles present minimal problems, angles less than 60 degrees become significantly more dangerous. Measures that can address this issue include creating parallel, but separated bicycle facilities, bicycle-only signal phases, left turn pockets, and "jug handles" that position bicycles at a 90-degree angle to the track.

Technology of the streetcar has come a long way to meet the changing needs of an urban environment. Not only are they becoming more efficient and aesthetically pleasing, they are also meeting the growing need to transport more people in a safe and effective manner.

This article is co-authored by Rhonda Bell, an Urban Design and Landscape Architecture Senior Associate with RNL and Phil Klinkon, AIA, NCARB Pacific Region Transit Director at RNL (www.rnldesign.com).