Viewing a single comment thread. View all comments

pizzajona t1_j04ewq3 wrote

Reply to comment by sudsomatic in Are most people in Washington DC liking the new Metro connection out to Dulles Airport? by pizza_4_all_

Apparently Metro did a study which showed express service would only save about 7 min from Dulles to downtown.

Something that can be done now would be to increase Metro’s top speed from 59mph to 75 mph. This would help a lot on the silver line because it runs in highway medians for so long. The operating speed was lowered after a near-fatal incident.

11

sudsomatic t1_j04h6mq wrote

I thought that study said 7 minutes savings was if they don’t have a third rail because it would just catch up to the train in front.

6

SandBoxJohn t1_j04ofiv wrote

The only logical way to shorten the runtime to Dulles is to build a track that would bypass the 4 Tysons Corner stations and upgrade the signaling system to allow closer headways, As built the Silver line is limited to 19 train per hour.

3

SandBoxJohn t1_j04mk9r wrote

WMATA lowered maximum speeds long before what is stated in that Washington Post article. Rolling stock performance profiles were detuned back in the mid 1990s (reducing acceleration, deceleration rates and top speed) when stress cracks were found in the 1k car bodies and to prevent them from forming in the nearly identical 2,3 and 4k car bodies.

3

pizzajona t1_j04nap2 wrote

So what was the top speed before 2016?

1

SandBoxJohn t1_j04ptal wrote

Typically below 65 MPH as it took longer to accelerate to the higher speeds before needing to decelerate into the next station.

2

aDCperson123 t1_j04qizd wrote

Given the steel construction of the 7/8ks once they retire the Al cars would they maybe consider retuning?

1

SandBoxJohn t1_j04vtca wrote

It will likely not happen as running the trains like scalded dogs will shorten their service life in much the same way as what happened to the 1 and 4k cars.

1

aDCperson123 t1_j053y5s wrote

I just figured the fatigue properties of the alloy might be enough different to handle the stress. At some design limit of course it would be. It totally depends on the metallurgy and sizing.

2

yunnifymonte t1_j04z3eg wrote

Shorten their Service Life? I’m confused, I agree about the 4000 Series, but about the 1000 Series, weren’t Metro supposed to retire them earlier, but couldn’t due to a Railcar Shortage, Pre-7ks?

1

SandBoxJohn t1_j06d8po wrote

The 1k cars were designed for a service life of roughly 40 years. They began developing stress cracks in their car bodies at roughly half the length of their service life. They were for all practical purposes beyond the end of their service life before reaching 40 years.

2