As part of its effort to clean up the air and comply with EPA regulations, an eight-county area covering Houston and its hinterlands is now under a 55 MPH speed limit. Some folks are not too happy about this, saying that lower speeds will have no effect. Naturally, officials defend the science behind the lower speed/fewer emissions link.
I'll stipulate the benefits of driving 55 MPH - it's safer, it burns less fuel, and yeah, it's more emissions-efficient. I'm a leadfoot, so this is gonna be hard on me, but I'll try my best.
Of course, I wouldn't bother blogging about this if I didn't have some gripes. First off, I can't help but think that the real problem is with jammed freeways during our everlasting rush hour. Surely going 70 MPH is better on the air than stop-and-go driving. And speaking of stop-and-go driving, don't get me started on Houston's bizarrely unsynchronized and poorly timed traffic lights. I'd like to see more light rail plans and better traffic light management before I'm willing to make nice about driving slower.
One nice thing about this is that I have yet another reason to feel smug about not driving an SUV:
In general, the lighter a vehicle and the smaller and cleaner its engine, the less improvement in pollution from a lower speed.
As a group, [Randy Wood, deputy director for environmental policy at the Texas Natural Resource Conservation Commission in Austin] said, heavy-duty vehicles, including big trucks and larger pickups and sport utility vehicles, release about 10 times the [Nitrogen oxides, called NOX for short] per mile as light-duty vehicles, which include cars and smaller pickups and SUVs.
The 55-mph speed limit is part of a two-prong plan to cut vehicle emissions, which the H-GAC estimates produce 24 percent of NOX emissions in the region.
The other prong, certain to also elicit howls of complaint from motorists, is a tightened tailpipe testing program scheduled to begin May 1.
The slower speed limit is projected to account for a NOX reduction of about 12 tons a day, the tailpipe test about 36 tons. Together, they would achieve about 7 percent of the needed reductions, set at 750 to 800 tons a day under the state's air plan.