Here is a look at some of the transportation headlines gathered by us and the Metro Library. The full list of headlines is posted on the library’s blog.

New census numbers confirm resurgance of cities (Sustainable Cities Collective)

Not exactly surprising news, but the blog has a nice breakdown of new Census data showing that a lot of growth in cities is coming from the urban core of many metro areas. And data suggest that in one city — Atlanta — wealthier people are moving back to the city and into older homes instead of moving back into fancy new places. Interesting stuff and the re-urbanization of America should certainly be good for mass transit. If, that is, funding follows the trends.

BART studying operating hours (SFBARTblog)

On weeknights, BART is only closed for two-and-a-half hours — from 1:30 a.m. to 4 a.m. At the same time, patrons frequently ask for trains to run past 1:30 a.m. on weekend nights. Problem is, the agency has very little downtime to do needed maintenance work. As a result, the agency is going to look at the hours it runs and see if perhaps there’s another way meet demands of passengers. The 4 a.m. start date is going to get another look — it was started after the Loma Prieta earthquake to help people reach jobs because of damage to freeways.

Scientists weigh in on polar bears in a warming world (New York Times)

A fascinating post on the NYT’s Dot Earth blog about the retreat of older, thicker sea ice that is preferred habitat of polar bears in the Arctic. Optimism is in short supply, although there are still disputes within the scientific community over exactly how and when global warming is threatening polar bears. The bottom line, though, is that mortality is up and over time that will have a corrosive effect on bear populations. Attentive readers of The Source already know there’s widespread agreement among many scientists and governments that there’s a direct link between what comes out of your tailpipe and global warming.