ION Phase 2 - Cambridge's Light Rail Transit

[trainspotter139]

Cut and cover is about 3x more expensive, costing about $150M/km on average compared to surface rail which costs $45M/k.


Except it's not just "a few metres" as you so blithely call it. The elevated approach to the CPR track that crosses Eagle St requires runs of 200m and 230m on each side to get high enough over the track. Since the roadway would need to be above the LRT track at least as much as the LRT track would need to be above the freight line, if not more to allow for the catenaries.

100m for the roundabout itself, for the full cut-and-cover section ($11M incremental), and then maybe 400m total of ramps down/up from the cut-and-cover section. The cut is lower there, and no covering, so it should be less than half the cost on average. If we assume half, that's another $21M incremental, for a total of $32M.

However, there would likely be some savings from signaling/traffic lights/etc as compared to using a level crossing at the roundabout. I have no idea on those costs, but they're not free, either. So, maybe it's an extra $30M in costs, using your numbers?

 A cut and cover for that particular location would be impractical and very, very expensive because of it's proximity to the Mill Creek. the ramps alone would put the cut and cover tunnel below the water line of the creek which would then require a large reservoir and pumping station underneath for flood risk mitigation and storm water management. That turns $30million into more like >$100million plus annual operating and maintenance costs.