New York City began its first day of fuel rationing Friday but there was relief for tens of thousands of people who got back electricity disrupted during superstorm Sandy.

Rationing was ordered in response to massive lines at gas stations, with cars carrying odd numbered license plates allowed to fill up on odd-numbered dates and even plates on even days.

Mayor Michael Bloomberg acknowledged in a radio interview that he didn't know if the scheme, already in place in New Jersey, would bring relief.

"There's no guarantee that odd/even is going to make a big difference. It's certainly not going to make for more gas," Bloomberg said. "In New Jersey, there is some evidence that the lines were shorter."

The US Department of Energy said that electricity outages were being steadily reduced, although power companies say that some neighborhoods will remain in the dark for many days to come because flood damage was so severe.

According to the latest figures, 434,140 homes and businesses remained without power across the region, down from 761,418 late Thursday and about 60,000 less than earlier Friday.

In New York State alone, the number was 201,865, or three percent of the total number of customers in the state. That was down from 343,211 customers on Thursday.

The Energy Department said that 28 percent of gas stations in the New York area still did not have fuel, but that this was down from 38 percent two days ago.

There was another glimmer of light for New York's transport system, with officials announcing the partial reopening of subway service to the Rockaways neighborhood on Sunday, as well as a temporary ferry service to the area, which was particularly hard hit during the storm.

Bloomberg, meanwhile, told a press conference that efforts to get people back into damaged homes were accelerating.

Public housing buildings that lost power during Sandy will nearly all "have the lights back on tonight or tomorrow. And by the middle of next week, all but a handful should also have heat and hot water," he said.

However, in isolated, tight-knit Rockaways, 40,000 homes and businesses were still in the dark.

President Barack Obama said he would visit New York on Thursday.

Sandy makes fuel the hot commodity in New York
New York (AFP) Nov 9, 2012 - Hurricane Sandy's most visible cost was the human suffering of flooded homes, but the damage of refineries, oil terminals and pipelines is having a no less severe impact by drying up the flow of fuel to motorists.

The superstorm hit the New York area back on October 29, and just figuring out what happened has been part of the challenge to getting the flow of fuel -- now rationed in both New Jersey and New York -- back to normal.

A week and a half after the storm, 28 percent of gas stations in the New York metro area were still without supplies and those that were functioning had long lines of customers.

Initially, the shutting down of petrol stations was blamed on power cuts which meant the pumps used by motorists couldn't work, but the problem quickly turned out to be far deeper and more difficult to address.

"Last week's storm hit the fuel network hard and knocked out critical infrastructure needed to distribute gasoline," Mayor Michael Bloomberg said as he announced Friday's rationing scheme.

"Even as the region's petroleum infrastructure slowly returns to normal, the gasoline supply remains a real problem."

An example of the infrastructure problems is that "gasoline terminals, places where the deliveries trucks come everyday to fill up with gas and take gas up to gas stations, are shut down," said Michael Green, at the American Automobile Association.

"As a result it is very difficult for the gas stations to receive new shipments of gasoline," he said.

Seven terminals remained closed on Friday across New York and New Jersey, the Department of Energy said. That creates a "bottleneck," Green said.

At the same time, two refineries in New Jersey that usually churn out 308,000 barrels of gasoline a day were still out of order due to flooding and electric outages.

As a consequence, east coast refineries that operated at 81% capacity before Sandy are now down to 58.5% capacity, and "those numbers reflect, quantify the severity of the problem," said Gregg Laskoski, analyst at GasBuddy.com, which follows gas prices.

Further downstream, electricity cuts also temporarily disrupted pipelines bringing refined products from the Gulf of Mexico to New Jersey terminals.

"Some of the pipelines lost power during the storm. As a result they were unable to pump gas and other petroleum products through the pipelines," Green said.

The storm also prompted a suspension lasting several days of petroleum imports from Europe to New York, since ships were unable to unload their cargo, analyst Robert Yawger at Mizuho Securities said.

And "you cant just make up for everything in one day," he added.

New York Mayor Michael Bloomberg said in a radio interview Friday he didn't know if the rationing scheme, already in place in New Jersey, would bring relief.

"There's no guarantee that odd/even is going to make a big difference. It's certainly not going to make for more gas," Bloomberg said. "In New Jersey there is some evidence that the lines were shorter."

However, the energy department said that the number of stations without gas was slowly decreasing, down from 38 percent two days ago.