Looking forward to a future when SMART has to provide more than occasional commute service ... can they do double track thru Cal Park Hill, or is that precluded by the trail in the tunnel? Obviously, they can't do double thru the tunnel north of downtown SR without building a bigger tunnel ($$$e07 or 08). Those spots, and trundling thru downtowns SR and Petaluma on single track at grade, will be bottlenecks should SMART ever have enough demand to consider real transit-level operation (trains every 15 min. or 1/2 hour in both directions most of the day). Until they reach that point, their traffic density probably won't justify wiring for electric operation, though at some point Tier-4 diesel will no longer be good enough and something will have to be done about local emissions which could trigger electrification of some kind before operating needs do.