Railroad Forums 

  • Heavy Rail Transit grade crossings

  • General discussion of passenger rail systems not otherwise covered in the specific forums in this category, including high speed rail.
General discussion of passenger rail systems not otherwise covered in the specific forums in this category, including high speed rail.

Moderators: mtuandrew, gprimr1

 #1397087  by MattW
 
I've heard that the FTA basically prohibits grade crossings for new heavy rail extensions, but most heavy rail extensions use third rail. Third rail isn't necessarily the issue as shown by the LIRR, MNRR and CTA (though two of the three are railroads, and the third's crossings are legacy), but would the FTA allow grade crossings if new HRT used overhead catenary instead of third rail? I'm guessing not due to the lighter construction standards, but they do allow lighter LRT vehicles to have grade crossings and at-grade segments.

Thanks!

Moderator's Note: edited thread title, 08/20/16
 #1397088  by DutchRailnut
 
why not, for example some of NJT lines have crossings and Catenary, so does MN New Canaan Branch.
 #1397092  by mtuandrew
 
I'd feel far more comfortable designing a railroad crossing with overhead wire than third rail. Overhead wire in some parts of America (Philadelphia CSX ex-Reading, off the top of my head; maybe NS around Jersey City?) is 20' off the ground, and you'd have to really try to hit that with a truck! You wouldn't have to try nearly as hard to weld your car to a 750 vdc third rail at fender level, even if it's 200 feet down the track.
 #1397183  by Jeff Smith
 
Catenary is superior for power transmission, so why not? DC requires a lot of sub-stations, and the MNRR Valhalla grade crossing accident revealed a risk likely not previously known. Unless you're limited by clearance (e.g. Park Avenue Tunnel to GCT) or legacy issues (New York Central or LIRR) why use DC anyway?
 #1397189  by DutchRailnut
 
Ok now your confusing things, DC does not just mean third rail, plenty of overhead power systems are powered by DC.
for example Metra in Chicago, and Dutch national railroads at 1500 volt DC and Italy, Belgium at 3000 volt DC.
And with AC propulsion the feed to inverters is DC, so in essence what AC catenary saves you in transmission cost, penalizes the weight on traction equipment for transformers and rectifiers.
 #1397196  by electricron
 
Yes, overhead catenary can be both ac or dc, but most, if not all, third rail systems used dc. I'm not aware of any third rail systems using ac, but there may be one I'm not aware of.

And I'll repeat this rule of thumb again just for FYI reasons, it takes 1kV per mile to push ac selectricity from a source.
So, on a 25kV catenary, gaps in the catenary can be up to 50 miles apart with the feed in the middle. On a 12kV catenary, the gaps can be up to 24 miles apart with the feed in the middle.

Also, on ac systems you see gaps because one can't guarantee synchronization of the different voltage supplies, while on do systems gaps aren't needed as long as the supply polarities are correct.

There are advantages and disadvantages for both ac and dc systems, but in general ac systems become better the longer the railroad corridor is.
 #1397242  by MattW
 
Perhaps I should have phrased my question better. The question really doesn't have much to do with the electrification. Really I'd just like to know if Heavy Rail is allowed to have grade crossings at all. I only mentioned the electrification because at one time I had heard that it wasn't allowed, but I don't know if that's because most HRT is third rail, or because HRT just can't have grade crossings regardless of power supply.
 #1397248  by DutchRailnut
 
only restrictions on Heavy rail and rail crossings is they are not allowed in territory where track speed exceeds 110 mph.
as for Catenary it can be installed high at crossings with physial truck clearance of nearly 25 feet high, 14'6" for basic single level and a pantograph reach of 10 to 12 feet.
 #1397257  by mtuandrew
 
MattW wrote:Perhaps I should have phrased my question better. The question really doesn't have much to do with the electrification. Really I'd just like to know if Heavy Rail is allowed to have grade crossings at all. I only mentioned the electrification because at one time I had heard that it wasn't allowed, but I don't know if that's because most HRT is third rail, or because HRT just can't have grade crossings regardless of power supply.
MattW, are you talking subway-style opposite-of-Light Rail Transit, like the Chicago L or the Washington, DC Metro, or are you talking FRA-compatible common carrier railroads like Amtrak's NEC?
 #1397276  by MattW
 
mtuandrew, yes, I am, more specifically Atlanta's MARTA. But, if the proposed extensions used catenary. So basically the MBTA Blue Line north of Airport, or Cleveland's Red Line. It's still heavy rail, but it's using catenary; would public, revenue-trackage grade crossings be allowed? What triggered this general question, is the new MARTA car order. MARTA's own RFI indicates the possibility of pantograph capability and some of us are debating if that means they're looking at allowing grade crossings on any of the planned extensions.
 #1397411  by mtuandrew
 
Interesting question, MattW.

I'm inclined to say that MARTA could include grade (level) crossings, but that would pretty much throw their Automatic Train Operation out the window. Chicago has a number of grade crossings on its outlying branches, all with third rail, but they may be the only such American system with grade crossings. New York's last crossing was eliminated ca 1973, and I can't see any others on heritage (Boston, Philadelphia), "bicentennial" (SF BART, DC WMATA), or new-build (LA, San Juan PR, Miami) systems.
 #1397421  by bdawe
 
mtuandrew wrote:Interesting question, MattW.

I'm inclined to say that MARTA could include grade (level) crossings, but that would pretty much throw their Automatic Train Operation out the window.
I believe Muni Metro is ATO inside the Market Street Subway, despite being light rail/streetcar operation outside of it, so presumably you don't have to abandon ATO to have manual operation segments
 #1397531  by ExCon90
 
True--a train coming from Caltrain or the "T" must stop on the ramp leading to the tunnel portal, then "advance and be recognized" before getting a signal to proceed into ATO territory. For some reason this often takes a few minutes, but this is presumably a glitch that could be straightened out. For some reason it doesn't seem to be a problem for trains in the opposite direction at West Portal and Church & Duboce. I think I've read somewhere, however, that the FTA may simply be opposed to new grade crossings in principle, as MattW mentioned upthread, and with good reason considering the behavior of many motorists at grade crossings.
 #1397582  by bdawe
 
I was also under the impression that the FTA wasn't a regulatory agency, rather a funding agency like the FHA, and while they might whithhold support form operations they do not approve of, they don't regulate directly like the FRA