station platforms

It seems that most of the outdoor stations on metro have doors opening on the left side and there only seems to be a few stations where the doors on the right.

any idea why this is the case, and how come stations like arlington cemetary and eisenhower ave stations become the exception?

i sometimes wonder if metro should have made all stations island platforms so that they dont need to build doors on the right side at all, and just fill it with seats

I thought I read somewhere that one reason to NOT have island stations is crowding. By having the platforms on opposite sides you can better control crowding on the platforms and there is less 'conflict' as passengers embark and disembark trains heading in opposite directions. Now, that doesn't explain Eisenhower or Arlington, both of which are not crowded stations, or why Foggy Bottom is an island platform but then the ones further east are side platforms.

YOLO wrote: I sometimes wonder if metro should have made all stations island platforms so that they dont need to build doors on the right side at all, and just fill it with seats

In this proposal, you'd still need to have doors on both sides of the cars, UNLESS you are also proposing that instead of using switch junctions to place outgoing trains from terminals on the right track, you build a balloon loop beyond each terminal for turning trains.

YOLO wrote: i sometimes wonder if metro should have made all stations island platforms so that they dont need to build doors on the right side at all, and just fill it with seats

How would you have island platforms work at intersection stations like Metro Center and Gallery Place? It could be done, but at a price in complexity and cost in the station configuration and access capacity. An upper level with side platforms and a crossing lower level with an island platform works quite well. Island platforms appears to be the preferred configuration, but there are obviously stations where the constraints of space & existing infrastructure and track spacing led to side platforms.

Cars with doors on only 1 side would present all sorts of constraints and headaches in operational use.

"YOLO"
It seems that most of the outdoor stations on metro have doors opening on the left side and there only seems to be a few stations where the doors on the right.

any idea why this is the case, and how come stations like arlington cemetary and eisenhower ave stations become the exception?

The reason why the system is populated with more island platform station then twin platform is purely economic. Island platform stations are cheaper to build, operate and maintain because they require fewer escalators and elevator between the mezzanines and platforms.

i sometimes wonder if metro should have made all stations island platforms so that they dont need to build doors on the right side at all, and just fill it with seats

The existence of the hand of full of twin platform stations is again economic. The condition of the environment at those sites made it cheaper to build twin platform stations. There were other factors as well. In the case of Arlington Cemetery and Eisenhower Avenue, smaller footprint. Tapering to 40' track centers in the approaches to the station as apposed to 14' track centers. In subway the determining factor is station depth. Cheaper to build cut and cover twin box tunnels between stations then deeper bored tunnels to accommodate island platform stations.

As other have pointed out turning loop would be needed at the end of lines to accommodate doors on only one side of the rolling stock. Single tracking would be imposable. Short turn terminals would be economically unfeasible.

There isn't a single passenger rail operation anyplace on the planet that I know of where the rolling stock has doors on only one side with the exception of the hand full of legacy streetcar systems that use right hand loading.

oops, didn't think about single tracking and reversing trains.

Your explanation makes sense for Cheverly and Eisenhower Ave but I'm still confused regarding arlington cemetary - aren't the tracks that come out of the north tunnels separated apart and can easily accomodate an island platform?

"YOLO"
oops, didn't think about single tracking and reversing trains.

No biggie.

Your explanation makes sense for Cheverly and Eisenhower Ave but I'm still confused regarding arlington cemetary - aren't the tracks that come out of the north tunnels separated apart and can easily accomodate an island platform?

The tunnels south of Rosslyn taper as they approach the portal, at the portal the track centers are roughly half the distances apart needed to accommodate an island platform. The tunnels form the Pentagon station to the portal are twin box cut and cover tunnels, they began their taper and elevation change before the curve leading to the junction north of the station.