The VTA will do NOTHING for North County. Nothing. You have been fooled again.

Mountain View should get "extra credit" for only wanting to separate one crossing - Rengstorff, while Palo Alto may want to do 3 or 4.

Mountain View does satisfy the VTA requirements of keeping the rail line at grade while roads, bike ways, and pedestrian ways will pass under the tracks. At Rengstorff crossing, all three modes will go under. At Castro crossing, no roads will cross ... just a bicycle and pedestrian way will go under.

John and Mike, I hope you are right about this. Over or under is perfectly doable, and I think (don't know the engineering studies) less expensive. Does Palo Alto want to suck up ALL THE AVAILABLE MONEY for their own buried train line? Then let them tax themselves and foot the extra construction costs! Simple. (but it's politics - so it is never simple).

Under - just look at the pedestrian underpass @Caltrain stop on the border of PA and MV (goes over to Google's complex and connects Monta Loma area to the San Antonio retail/commercial/residential complex). This is not rocket science, just good civil engineering/civic planning. Built 'before my time' here.

Over
A modular construction design, of precast concrete columns and manufactured steel bridge beams (look at some freeway overpasses) that was uniformly available throughout the area, could significantly reduce costs. Only local foundation engineering would need to be done. (but regional government Never works this way!)

"A modular construction design, of precast concrete columns and manufactured steel bridge beams" is always a wonderful addition to any community. Just "look at some freeway overpasses".

In the land of the nerd, many look but do not see.

Tunneling is ludicrous. It's not even necessarily possible if the water table is too high or lowering the railroad that much would require excessive gradients.

Depression (trenching) is a possibility, is attractive since it hides and quiets the railroad. (For a freeway it's great, too, and the on- and off-ramps are appealing in a scientific sense since they use gravity with rather than against their users.) The Caltrain right-of-way may have to have vertical trench or partial-trench walls where it's especially narrow.

A full raising of the railroad above road and trail height is acceptable, as is an aerial structure or viaduct, as with Prague's New Connection (four tracks) or the BART East Bay viaduct (but larger). A viaduct can even be built over a trench for more capacity.

A "hybrid" crossing as in San Carlos, with the railroad slightly elevated and roads and paths slightly depressed as needed, is a good idea, as is the reverse (partial depression or trench, partial elevation of crossings by roads and trails).

It ought to be the same for as many crossings on the Peninsula as possible and keep the railroad to the same height as much as possible. Good luck, whatever is tried.