Scottsdale has joined the regional agency responsible for light-rail planning, a move intended to give Scottsdale an opportunity to participate in a study that will look at the merits of running light rail, streetcar or other transit uses through the city.

The City Council voted 4-3 Tuesday to join Valley Metro Rail, or Metro, once again opening up the light-rail debate that has surfaced numerous times since the transportation master plan update was launched in 2005.

In December, the council as part of its discussion on the transportation plan agreed to become the seventh city to join Metro. Councilman Bob Littlefield cast the only dissenting vote at the time.

In Tuesday's vote that made the decision official, Littlefield was joined by Councilmen Jim Lane and Tony Nelssen in dissenting.

Supporters of joining Metro said this was being done to keep options open and have a seat at the table with neighboring communities as transit decisions are made that will affect Scottsdale. They stressed that a vote of the public would be held before light rail were ever approved in Scottsdale.

"There will never, ever be a light-rail project ever in the city without all of us voting as a community," Mayor Mary Manross said.

But those opposed said the vote was one more step toward bringing light rail or streetcars to Scottsdale.

"This is symbolic because what this is about is getting Scottsdale committed to light rail," Littlefield said.

The city's cost to join Metro will be $50,000 a year. The city will pay $16,667 for the remainder of this fiscal year, plus $50,000 for 2008-09. Scottsdale will join Phoenix, Tempe, Mesa, Glendale, Chandler and Peoria as members of the board.

Metro spokesman John Farry said Scottsdale would have about a 3 percent weighted vote, like Chandler and Peoria. There are no approved extensions into the three cities, but each borders a city where a current line or extension is approved.

Farry said a discussion about Scottsdale's wishes will take place once the city joins. The next Metro meeting is scheduled for April.

Today, the Tempe South study, which includes Tempe and Chandler, is under way.

Scottsdale needed to join Metro if there was any chance the study was to be amended to include Scottsdale, or a new one created specifically for the city.

Today, the study is limited to an area south of the Red Mountain Freeway stretch of Loop 202.

It will study a number of transit options, including light rail, streetcars, bus rapid transit and commuter rail in the area where voters have already OK'd an extension.

The initial 20-mile light-rail line through Phoenix, Tempe and Mesa is scheduled to open in December.