Why does Santa deliver only at night? The answer in New York City is obvious. If he worked any other way in this impossibly congested place, he'd still be delivering our presents in June.

Traffic is that bad.

The average speed on a midtown street during business hours is between 7.2 and 8.2 miles per hour. The specific reasons why aren't that hard to spot.

Taxis and buses inch along fitfully with frequent long stops. Then there are the trucks. More than 100,000 of them rumble into Manhattan every business day, reducing most cross-streets to a single lane of slug-like traffic as they double-park to make deliveries.

The result is chronic gridlock and its ugly by-products: dirty air, lost productivity and a freight system that dearly costs truckers and the businesses that depend on them.

There is a better way.

The city's Department of Transportation a few years ago launched a pilot program that encouraged Manhattan business managers to switch their freight deliveries from regular business hours to slots between 10 p.m. and 6 a.m.

It worked. Shippers found they could make deliveries on schedule, without wasting fuel or racking up thousands of dollars in parking tickets and overtime. Companies -- in particular restaurants -- found they no longer needed to overstock perishables in case the truck was late.

If expanded, the off-hours delivery program could mean cleaner air and less daytime traffic.

The city DOT is looking for ways to make a permanent program happen, and we hope it succeeds.

The catch, of course, is that some businesses would have to keep a worker on duty during the off-hours to receive deliveries. The DOT is exploring the possibility of offering tax incentives to participating companies.

The DOT is also exploring ways to mitigate noise. That's crucial. Nothing will kill the program quicker than residents furious over trucks idling beneath their windows in the middle of the night. Santa solved the problem by using reindeer. Too bad the rest of us can't.