San Francisco’s N-Judah Muni Metro line shows design option for light rail in Austin’s Guadalupe-Lamar corridor9 December 2014
In recent years, critics of installing “urban rail” — i.e., a light rail transit (LRT) line — in the Guadalupe-Lamar (G-L) corridor have endeavored to portray this potential project as an impossibly daunting task, contrary to many years of local planning to do just that. The predominant contention is that these two busy major arterials are simply too narrow to accommodate a double-track LRT alignment on dedicated lanes while maintaining adequate general traffic flow, and that introducing LRT would require either heavy civil works construction, or extensive, costly acquisition of adjacent property to widen the right-of-way (ROW), or both.
However, the G-L travel corridor — most central in the city — actually carries the heaviest travel flow of local arterials, serves the highest-density neighborhoods; and connects the most important activity clusters; thus, ultimately, given the inherent constraints of motor vehicle transportation, some type of high-quality, high-capacity public transport alternative is essential to maintain long-term mobility. Fortunately, there are LRT alignment designs that would facilitate fitting affordable, cost-effective, surface LRT into these arterials, while maintaining at least four lanes of general traffic capacity through most of the corridor.
While this corridor is characterized by an unusually narrow roadway structure — much of both North Lamar Blvd. and Guadalupe St. have total ROW (including sidewalks and curbs) just 80 feet wide — there appears to be adequate ROW width to install dedicated LRT lanes, within a 24-foot reservation, without additional ROW acquisition (easements), together with four traffic lanes (two 10-ft lanes per direction) for most of the alignment, plus sidewalks and curbs (8 fteet) on each side.
For stations, relatively short segments of additional ROW would need to be acquired — approximately 20 feet of width for 300 feet (about one block) on each side of major intersections intended as station sites. Acquiring wider ROW would also be useful along sections of Guadalupe St. (particularly where the proposed LRT alignment runs adjacent to stretches of state-owned land). Within the Drag section of Guadalupe (W. 29th St. to MLK Blvd.), dedicated LRT lanes could remain in the center of the arterial, with some reconfiguration of traffic lanes and other facilities.
ROW constraints will impact the traction electrification system (TES) and overhead contact system (OCS) design in the G-L corridor. (OCS is the commonly used term for the overhead power wire system; it can be catenary or a simple, single-trolley-wire design.)
Appropriate design of the TES is critical to the narrow overall alignment design required in this corridor. Unlike many other modern new-start LRT installations, for OCS power wire suspension this alignment design would eschew TES center poles (masts) with bracket arms. Instead, to facilitate adequately narrow LRT ROW, this design would use an alternative design whereby the OCS would be carried by cross-span cables suspended from side poles inserted at curbside. Examples of this type of OCS suspension can be found in other LRT installations, such as in Houston, San Diego, and San Jose. (Whether OCS is simple trolley wire or catenary-type suspension would not affect this aspect of alignment design.)
The following schematic diagram illustrates a cross-section of this design for the majority of both North Lamar and Guadalupe, with LRT running in a dedicated reservation, two traffic lanes on each side, and sidewalks shared by pedestrians and bicyclists on each side.
For such a configuration of an LRT reservation within a major arterial, constrained by narrow ROW width, San Francisco offers perhaps the closest operating example with the N-Judah Line of the Muni Metro LRT system that branches westward from the city center. For a roughly 10-block section along Judah St., from about 9th Avenue to 19th Avenue, LRT tracks are laid in a raised dedicated reservation that isolates them from motor vehicle traffic; eliminating the need for additional barriers such as channelization buttons or other separation devices, this design has the benefit of minimizing horizontal clearance.
As the photo at the top of this post illustrates, despite a ROW constraint of just 80 feet, this configuration of the major Judah St. arterial is able to provide the raised LRT reservation plus 4 motor vehicle lanes plus parallel sidewalks. It should not be difficult to envision a similar design working in Austin’s Guadalupe-Lamar corridor.
In the overhead view shown in the photo below, the top of a Muni Metro train can be seen in the center, running on the upper of the two tracks in the reservation. The different allocation of ROW space for traffic and sidewalk can be noticed — San Francisco provides an on-street parking lane and a traffic lane on each side of the arterial, plus sidewalks nearly 11 feet in width. In contrast, Austin Rail Now recommends that Guadalupe-Lamar would have 4 full traffic lanes of 10-ft width, no parking lanes, and 8-ft sidewalks.
The following two photos at surface level showing Muni Metro trains in the Judah St. reservation further suggest how efficient LRT service can be installed in the relatively constrained arterial ROW of Austin’s Guadalupe-Lamar corridor.
There are other alternatives for installing LRT in the Guadalupe-Lamar corridor. To eliminate the need for TES poles, for example, there are “wireless” power options, but these tend to be proprietary, somewhat experimental technologies and substantially more expensive. Widening these arterials by acquiring more ROW is another option, but this also introduces greater expense. We believe that the raised-median design, with side-mounted TES poles, presented here, represents a particularly cost-effective, functional solution worth considering for G-L and other major Austin corridors. ■