HONOLULU -- Honolulu City Council members on Wednesday got their first chance to grill Mayor Mufi Hannemann's administration on its new study that favors a new rail transit system that could cost more than $5 billion as the best way to ease Oahu's traffic situation.

The city's transit alternatives report, which was released this week, favors a fixed rail system for Oahu with two possible routes: a 20-mile system between East Kapolei and Ala Moana or a 28-mile route between Kapolei and Manoa.

When connecting bus and other costs are factored in, the report shows the bill for the shorter route would be more than $4 billion and the longer route more than $5 billion.

"My concern is the numbers don't seem to add up. The costs keep going up," Councilman Charles Djou said.

Djou, an opponent of rail transit, was the first to grill the administration.

"I would just like to know what happens if we don't get it. I mean, what happens if we are $100 million short?" Djou said.

Councilwoman Barbara Marshall was concerned about the city's estimate of 40,000 to 50,000 rail riders a day.

"Even if it is a good guess, it doesn't seem very much for the money," she said.

Councilman Romy Cachola said he is worried about even higher costs if they city has to issue bonds to cover shortfalls.

The next step now is the council will hold a series of 10 meetings both at City Hall and out in the public before it makes its final decision by the end of the year. However, many expect that the council will go with a fixed rail transit system.