One point that seems to be misunderstood about "Light Rail" is that the Light refers to the VEHICLE, NOT the weight of the rail. A LRV (Light Rail Vehicle) is a Lightweight rail VEHICLE, as opposed to a heavy rail vehicle such as a locomotive pulled train.
Doug
May your flanges always stay BETWEEN the rails
But again, some heavy rail vehicles are lighter than some light rail vehicles. The average Chcicago elevated or rapid transit, CTA, car weighs less than any Portland, OR or Dallas or Houston light rail car. Maybe not on a linear foot basis, because the light rail examples are three truck articulated cars and the CTA car is a 48-foot double truck car. But CTA is heavy rail because it is almost entire (now entirely except for the Brown Line) grade separated, uses equipmen not very well adaptable to street running or at least loading and loading passengers on the street, has very little if any single-car operation and runs long trains, whereas Houston and Portland and Dallas do run on the street, even if the lanes are rail or transit-only, have off-hour single-car operation, very little operation with longer than two-car trains. So it is called light rail. Typically, heavy rail equipment has end doors allowing crew, sometimes also the passengers, to pass from car to car. Typically, light rail had no more need for end doors than a bus. Many of the classic systems had both, sharing the same tracks, including Pacific Electric and Illinois Terminal. One example of heavy rail and light rail shearing the same tracks is between Cleveland Union Terminal and East 55th Street. The East-West rapid Red Line to the Airport is defined as heavy rail, even though has not generated the business to run long trains, and the Shaker Heights blue and green lines are defined as light rail, even if the actual vehicles are probably about as heavy as the red line cars. The red line loads from high platforms and the green and blue from sidewalk level with low-floor cars. Separate platforms are provided at the Terminal and at East 55th Street.
In 1903 the Brooklyn system attempted to extend an elevated line out over the streetcar tracks on Brooklyn and Queens first electric streetcar line from Cypress Street to 168th Street Jamaica. The open gate el cars had traps and steps (and most were probably conversions from steam-hauled coaches.) Some objections due to horses being scared and noise stopped the operation and normal streetcar service returned, lasting until 1947 even after the elevated structure was extended out to 168th above the streetcar tracks. (Now the structure has been cut back and the heavy rapid transit trains, the J and Z lines, routed into a new subway under parallel Archer Avenue with its last stop directly at the Long Island Railroad Jamaica Station.) Meanwhile, on what is now Macdonald Avenue and was Graves End Avenue, streetcars, elevated trains, and summertime steam trains shared the same track to Coney Island.
Sure you're not looking at a european speedometer in kph? 120kph=72mph, still not shabby.
Back to Minneapolis-St.Paul, a direct service downtown-to-downtown might save 3-4 minutes at 100mph rather than at 55mph non-stop. Then you need another line to make local stops; and I assume there is a lot of travel demand along the line. The high-speed line could extend beyond the downtowns to numerous outlying terminals over more conventional lines with stations and bus feeder connections.
A 100mph line is the first problem. Allowing as much as 4 inches superelevation and 3 inches underbalance, a 1-degree, 5,730-foot radius curve is the minimum necessary. How much money is there to buy the property and bulldoze a new line across the two cities? You don't want an LRV to hit or be hit by a truck at 100mph; so you need a fully grade-separated line.
The next problem is getting a compitent contractor to build the line. The Dan Ryan and O'Hare extensions were supposed to be 70mph lines that would suck all the riders off the commuter railroads. Instead, the Chicago Transit Authority rail lines deteriorated rapidly and suffered continually developing slow orders for decades. Having watched the track work progress for these extensions, I wasn't surprised by the outcome. The current crisis is only the most recent chapter in this affair.
Another problem is that a 100mph train will take 3-4 times the power and energy than for a 55mph train.
Can anyone point the way to a recent evaluation of light rail and bus rapid transit alternative costs on an annualized basis?
At "Gopher Rail" (Univ. of MN model railroad club's annual meet/convention) one of the guest speakers was from the company that is doing the engineering work for the light rail in the Twin Cities. IIRC he said that they had originally planned for the light rail on the Hiawatha line to go 50-55 MPH but ended up settling with 40-45 MPH because there was concern over the road/rail grade crossings...apparently Minneapolis city officials feared if the trains were going too fast, they would get to the crossings just as the crossing arms were fully down, they wanted to have a little more time to be sure the road was clear of traffic. Plus the stops are fairly close together, the train would hardly be getting up to 55 before it would have to brake for the next station.
The line between the Mpls and St Paul downtowns is going to involve some street running so it won't be going too fast. It will probably be about like the current bus service, 20-30 minutes downtown to downtown.
The 11 mile, 15 station Central Line suggests distances between stations would allow trains to reach 55 mph. With much of the line in street reservations with frequent intersections and crosswalks, only 40-45 mph may be appropriate. Conversely, if the line eventually will be extended beyond the respective downtowns on private rights-of-way, higher speed capability, 55-65 mph, would be desirable.
The concern for gates not lowering in time ignores predictive activation technology.
People keep arguing about the mechanical capability of light rail.
You need to remember that when running near capacity, 75% of the passengers are standing. Acceleration, deceleration, and curves must take that into account.
Here in Charlotte, the Siemens Low Floor S-70s are stopping about every half mile. There are 15 stops in less than 10 miles. At the far end, they are farther apart, in city center, some of the stops are about twice the length of the train apart. That is what limits the speed.
The farther apart the stops, the faster they can go, but the farther apart the stops, the less usefull they are as urban transport. A balance between the two determines the line's average speed.
Dave
Lackawanna Route of the Phoebe Snow
I have to take exception to the statement that the farther apart [the stops], the less useful [light rail is] as urban transport. I see the flexibility to meet changing land use and development density from urban to suburban to exurban as an advantage.
Light rail has limited capacity compared to heavy rail. LRT can meet lower travel demands in outlying lower density suburban areas without the cost of heavy rail. In some instances lrt has been built as a pre-metro and converted to rapid transit as land use densities increased.
Relatively compact urban centers impose limited and acceptable travel time penalties with surface running while providing high accessibility. The slow travel in the city center is offset by faster running in outlying areas on private rights of way. Development desities often are inadequate to generated any reasonable ridership to support closely-spaced stations. Ridership relies on bus feeder services and parking.
In an earlier posting I submitted what might be the minimal acceptabe curvature standard for a 100 mph LRT service with standing passengers, 5,730 feet. For an example, a more acceptable curve may be 8,511 feet radius. The point in that finding an alignment allowing such broad curves between Minneapolis and Saint Paul would be almost impossible.
I can only speak of the one system I use, but during rush hour our light rail runs every 7 1/2 minutes in each direction. Trying to squeeze an express in there would be a nightmare, and would not save more than a few minutes anyway. It's currently only 25 minutes end to end. That's an average of about 30 MPH including stops. You couldn't possibly save enough time to offset the cost and complexity. It's already faster and far less aggravating than driving the road that it parallels.
Based on current SEPTA schedules, the end to end run of a Norristown High Speed Line takes 28 minutes (limited stops between Ardmore and 69th Street Terminal). At a line length of 13.4 miles, the average speed is about 28 mph.
The N-5 cars have a high HP per axle rating, but I'd be guessing at the max speed between stations.
Blue Streak 1,
You mention holding a local 1-1/2 minutes for an express to arrive, then to follow it out.
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