As an experienced designer of streetcar systems, one question I am frequently asked is, "Can a streetcar _____?" The blanks are usually filled with design challenges, such as "turn left from a curb lane", or "go under a low clearance underpass" or "operate at higher speeds and frequencies." More often than not, the answer is YES! Modern streetcar systems, such as those operating in Seattle, Tucson, and Atlanta, are modeled after European trams that are designed to fit within tight, complex, and built-out urban environments. The unique combination of vehicle's size coupled with the ability to operate in the same lanes as automobiles, trucks, and buses allow designers to create safe, efficient solutions to nearly every design challenge that arises.
Tucson's Sun Link streetcar. Photo courtesy Terry Nash
3 min to read
Tucson's Sun Link streetcar. Photo courtesy Terry Nash
As an experienced designer of streetcar systems, one question I am frequently asked is, "Can a streetcar _____?" The blanks are usually filled with design challenges, such as "turn left from a curb lane", or "go under a low clearance underpass" or "operate at higher speeds and frequencies." More often than not, the answer is YES! Modern streetcar systems, such as those operating in Seattle, Tucson, and Atlanta, are modeled after European trams that are designed to fit within tight, complex, and built-out urban environments. The unique combination of vehicle's size coupled with the ability to operate in the same lanes as automobiles, trucks, and buses allow designers to create safe, efficient solutions to nearly every design challenge that arises.
Every streetcar system in design, construction, or operation today has faced a number of design challenges. Seattle is constructing a second line that operates on streets that have overhead trolley bus wires. Portland found creative solutions for accommodating bicycles safely alongside stations. Tucson had to traverse a low-clearance underpass. Dallas had to find a way to construct a line across a historic viaduct without adding overhead contact wire support poles. Salt Lake City was faced with a narrow right of way that prevented a double track mainline. All of these challenges were overcome with the goal of creating a cost-efficient system that minimized negative impacts to the built environment. In each of these examples, the adaptability and technological advancement of streetcar design solved the challenge:
• Streetcar lines built in mixed traffic lanes must operate like other vehicles, stopping at red lights and yielding to other traffic when necessary. But in some instances, streetcars must travel across lanes to make safe turns according to the route. This can be safely accommodated by detecting the streetcar separately at traffic signals.
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• By being 'fixed' to the rails, streetcars have a defined path of travel that can be easily delineated for clearances and safety. This allows drivers, pedestrians and bicyclists to see and understand exactly where the streetcar path lies.
• Streetcar manufacturers are promoting vehicles that can operate without the presence of an overhead contact wire (batteries, etc). This allows streetcar designers to plan routes through low clearance underpasses, around trolley bus or other sensitive overhead wires, and through segments where poles cannot be placed.
• Streetcar vehicles are derivatives of light rail vehicles. This means they feature level boarding at platforms and can operate at higher speeds, if provided the adequate track alignment to do so. Streetcars can switch between mixed traffic and exclusive guideways and adapt to the speeds and operating conditions of each with ease.
• Streetcars can operate in travel lanes along the curb, median, or in a separate trackway. Doors on both sides of streetcar vehicles allow stations to be placed on the left or right side of the tracks. This in turn allows designers to place tracks that minimize impacts to existing features, such as utility lines.
As more and more streetcar systems are designed, constructed, and opened for revenue service, the library of examples becomes larger. I would encourage decision-makers to explore these systems. You will likely find a similar, if not exact, example of a creative solution to these intimidating design challenges!
About the author Terry Nash is an associate VP in HNTB’s Santa Ana office. He has eighteen years of experience in rail transit projects, with an emphasis on streetcar and light rail in urban environments. He has led a variety of planning, design, and management roles on projects around the country, such as Tucson SunLink Streetcar, Valley Metro Rail in Phoenix and Tacoma Link in Seattle.
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