Riding your bike or walking instead of driving reduces carbon emissions by nearly one pound of CO2 per mile. (EPA) Buzz about Carmageddon--the closing of the 405 freeway in Los Angeles for the weekend--has reached fever pitch and become national news. (You know you've hit critical mass when Al Roker talks about it on the "Today" show.) Well, we're taking the opportunity to point out that fewer cars on the road is actually a good thing. For those in Los Angeles: we've got suggestions for ways you can take action this weekend (and avoid Carmageddon) on our City Carbon Index site.