It has its ups and downs, but Harald Buschbacher's idea might be the best of both transit worlds.
An august mayor of Toronto once said, "People want subways, folks… subways, subways. They don’t want these damn streetcars blocking up our city!” But subways are really expensive and take a long time to build. Streetcars or trolleys are cheaper, but get stopped at intersections by cars crossing. If they get special signalling, then they slow down cars.
Harald Buschbacher has a better idea that might be the best of both worlds. He calls it 'Low-clearance Rapid Transit' (LCRT) and tells TreeHugger that "it's about the idea of selectively grade free urban railway system offering nearly the quality of a metro [subway], but at costs closer to those of a tram [streetcar or trolley]."The concept is simple:
Step 1: Cutting minor crossroads. Minor intersections are replaced by protected pedestrian level crossings. Motorized vehicles can cross the LCRT line only on arterial roads.
This happens now in many cities where there are separated, dedicated streetcar rights of way.
Step 2: Selective grade separation. Most of the line length is on street level. Only in the area of intersections, the tracks are lowered in order to pass under the crossing road.
This is where it gets interesting. At the major intersections, instead of having special lights, the trolley dives down below the cross street.
Step 3: Reduced vehicle height. The LCRT vehicles are constructed for minimum height: the clearance of the underpasses is only about 2,5 m instead of usually about 4 m. This is possible through low-floor tram technology, allocation of technical devices at the ends of the vehicle instead of rooftop equipment and catenary-free operation in the underpass area.
Low entry trams are very common now, to make them wheelchair accessible. Now Buschbacher redesigns them to be low height, but putting the equipment at the ends instead of on the roof, and by dropping the pantographs when they travel under. He makes this work by having a pantograph at each end (and by having the trams longer than the tunnel), so that one can be touching the power source at all times. Another possible solution is batteries to get it through the tunnel, which is being done now on trolley buses.
Step 4: Steeper ramps. The ramps of the underpasses are steeper than those of conventional metros in part but the average slope is acceptable.
Here is where it gets interesting, with the trams diving underneath the major intersections.
Step 5: Elevated crossing roads. The underpasses are created not only by lowering the LCRT tracks, but also to some extent by elevating the crossing road. Thus, excavation and filling volume is reduced and technical effort for deep excavation is avoided.
They can even balance the fill and reduce excavation by making the crossroads go up a bit while the tram goes down. But basically, the tram now can run on a totally dedicated right of way without stopping for cars at intersections, at a fraction of the cost of tunnelling the entire thing.
Buschbacher's study goes on for over a hundred pages, looking at every possible permutation and problem. I regularly ride a tram that dips underground to meet the subway, and I worry that all the dipping and rising would cause problems for people with strollers and those standing. The option where the road also rises might cause visibility issues for drivers and would be lots of fun in icy conditions. Buschbacher says this is all within people's – and the vehicles' – tolerances.
But this could be so much cheaper and quicker than conventional subways, moving faster than a conventional trolley, and more fun than a roller coaster. We need more thinking like Harald Buschbacher is doing with his Low-clearance Rapid Transit. Read the whole study on his website.