TransLink Tracker Q2 2010-11

[somebody]

That's interesting, with a 1:50 limiting grade, you could only rise 4.4m in 220m, which wouldn't be enough.  1:30 brings it to 7.3m, which probably is enough.  I'd also wonder about putting a dip in the up suburban to reduce the height requirement possibly significantly.

I guess it's possible then, but it still requires a greater construction effort to connect CRR to Albion #3 & #4 as compared to Albion #1 & #2.  Maybe what may be in favour of the CRR team's plans is connecting to the mains may be doable on railway land, but connecting to the suburbans may be easiest to do by moving the up suburban to the east, possibly off current railway land.

Even if one track has to be messed with either way, attaching to the mains does mean a longer viaduct, so I wonder about this.

[Golliwog]

Putting a dip in the up suburban would work in the end, but I think would be much more disruptive as I doubt you would be able to acheive it in a single weekend closure. Theres more than just digging it out to the wanted depth, they have to make sure the soil down there is strong enough and then compact it before ballasting and what not can be done.

I think the land issue you outlined might be what it came down to. With how built up those blocks are, I don't think you could easily just take a portion, you would have to knock down the whole building.

I don't think in the scheme of things the longer viaduct would up the price too much. The Airport Roundabout Upgrade had a price tag of $327M, which was for a dual 750m viaduct over the Gateway motorway, a replacement for the gateway motorway overpass over the old roundabout, and replacement of the roudabout itself with the fast diamond intersection. I also expect a significant amount of the cost would be from having to maintain road access through the construction site. If the FG duplication is anything to go by, all thye have between the rail line and workers is a small barrier to seperate the two, and to my knowledge theres no speed restriction on the trains.

[mufreight]

The existing electrics should be able to cope with a grade of 1:25 on a flyover which would be a momentum grade of relatively short length anyway

[Golliwog]

Another question is how long is a standard signalling block? I know trains on the up suburban can get held just before the points for the FG flyover (and vice versa). Just curious as to how far back until its the previous block? I don't know much about signalling and how short the blocks are, but if where the new flyover comes down meant that trains on the up suburban had to be held where they would block access to the flyover, that could be an issue.

[somebody]

Another question is how long is a standard signalling block?

As long as you want to make it??

Longer blocks = worse headways, but cost saving.
Shorter blocks = better headways, more cost and more aspects required so that signaling doesn't provide a speed restriction on its own.

The existing electrics should be able to cope with a grade of 1:25 on a flyover which would be a momentum grade of relatively short length anyway

Indeed, and it looks like there is no reason to design it to handle EMUs which may not be on the network, and even if they are they could be sectorised out of that track.  That might make it more like 1:20.  Vertical curves may be the main limitation.

[mufreight]

The existing electrics should be able to cope with a grade of 1:25 on a flyover which would be a momentum grade of relatively short length anyway

Indeed, and it looks like there is no reason to design it to handle EMUs which may not be on the network, and even if they are they could be sectorised out of that track.  That might make it more like 1:20.  Vertical curves may be the main limitation.

The transition into and out of a vertical curve would not pose any problem with the controlling factor being the overall length of the rollingstock