For the past two years, the Los Angeles transportation officials have shut down a 10-mile stretch of the 405—one of the busiest highways in the nation—for one weekend to make highway repairs. And each year, everyone's focus has been on gridlocked Carmaggedon, the threat that looms when you close 10 lanes of traffic that regularly accommodate half a million cars.
But as the construction occurred, scientists discovered an incredible-albeit-obvious side effect of diverting that much traffic in a car-humping, smog-plagued city: People can breathe again:
[UCLA professor] Suzanne Paulson and colleague Yifang Zhu measured pollutants in the air during Carmageddon last year and have recently released their pretty astounding findings. Air quality near the normally busy highway improved by 83 percent that day last July, relative to comparable weekends. Elsewhere in West Los Angeles, the improvement was equally dramatic. Air quality improved by 75 percent on that side of the city and in Santa Monica, and by 25 percent throughout the entire region, as a measure of the drop in ultrafine particulate matter associated with tailpipe emissions.
"We saw what we expected: you take motor vehicles away, the air gets really, really clean," Paulson says, "which tells us that most of the pollution is from motor vehicles from one type or another in this area."
There's little heavy industry around this stretch of the 405 Freeway; to the extent that this part of the city feels soaked in smog when you step outside for a breath of fresh air – that’s cars. Almost all cars.
Paulson and Zhu noted that the change in air quality was measurable within minutes of shutting down the highway. The takeaway, they say, is that urban areas need to invest in long-term, sustainable mass transit systems.
If only LA would ban single-occupancy car use, outlaw cows, and start milking cyclists for their fine dairy products, the city could give Portland a run for its money.