From the Peak Oil board, someone asked about building more sheltered transit ways.
Based on this idea, we could take a look at the Finnish underground cross-country skiing complex.
The general idea being that underground facilities maintain a uniform year-around temperature, and packed snow would not melt too quickly.
A similar thing was proposed for the Twin Cities. I found a link to it, but it points back to the Finnish site only. In any case, it was going to cost an estimated $14 million dollars. Kind of a lot when you consider that a 3 year skiing pass costs $25 and the biggest booster is a ski shop owner.
From Minnesota Public Radio: Minnesota's recent warm winters have left ski-enthusiasts pining for the days of predictably snowy trails. Well, if Ahvo Taipale has his way, good snow cover will never be far away. Taipale, who owns Finn-Seesu Ski Shop in St. Paul, wants to build the continent's first underground cross-country skiing facility. He doesn't have a site picked out for the so-called "ski-tunnel" but he estimates it will cost about $14 million to build. Taipale says he visited the world's first ski-tunnel in Finland and thought the Twin Cities could use one too.
Next to biking, X-C skiing is the most efficient human-powered transportation. It probably ties with roller-blading under ideal conditions. But the whole covered or underground personal transit idea is a no go.