BandA wrote:So, if it is on completely separate tracks so no need for FRA compliance? Marta "heavy rail" (I assume heavy rail is lighter weight than commuter rail) uses 3rd rail; Are there any grade crossings? Is the ROW well controlled? Perhaps AC catanery would make more sense, or european DMU? Maybe DC catanery so it can switch to 3rd rail easily.
I'll admit I don't know which type of train will be selected, but let's review what the positives and negatives that will arise from the different choices.
1) Heavy Rail - what MARTA uses already.
Postives - uses the same equipment already in use means it's fully compatible.
Negatives - requires grade separation and double tracking the entire extension which is very expensive. Can't use the existing tracks in the corridor. Requires dedicated tracks. Requires electrification. FTA regulated, general transit regulations apply.
2) Commuter Rail - available either FRA compliant or non-FRA complaint.
Positives - it's cheaper because it doesn't require grade separation over the entire corridor. It can legally share the existing tracks in the corridor. It can use dedicated tracks if the freight railroad doesn't want to share tracks but is willing to share the corridor. Electrification optional. Existing freight customers can still be served.
Negatives - freight train interference with passenger trains on share tracks causing delays. Trains are usually heavier, uses more fuel. FRA regulated, general train regulations apply.
3) Light rail - what Charlotte uses.
Positives - required dedicated tracks, can't share tracks with freight trains, although it can share the corridor. Can be grade separated or not, but will need grade separation over or under freight tracks. Can make tighter curves, climb steeper grades. FTA regulated, general transit regulations apply. Almost all light rail systems uses DC traction. Light rail can share lanes with other traffic but usually uses dedicated lanes.
Negatives - requires electrification, usually by overhead cables. Trains are usually smaller in size than heavy rail.
If I were extending the MARTA line further than the airport station, I would use commuter rail in suburban neighborhoods. I would prefer using smaller DMU trains, either FRA or non-FRA compliant - if the airport was to be its terminus. I would prefer larger FRA compliant locomotive driven trains - if a downtown stations was to be its terminus. Trains heading all the way into downtown Atlanta would need to be larger to carry more commuters. In either case, commuter rail would be cheaper to implement than light rail or heavy rail, mainly because tracks can be shared and there's no need to electrify the corridor. Although adding electrification is still optional for powering commuter rail trains. I believe heavy rail using third rail for power is best used in urban neighborhoods with more available passengers, not in suburban neighborhoods with less people density.