A slowing economy continues to take a toll on tax collections needed to fund Honolulu's planned commuter rail system.

During February, net transit tax collections rose slightly to $13.3 million, versus the $13.2 million collected in February 2008, according to the state Department of Taxation. Despite the rise in collections in February, transit-tax collections overall remain below projections.

City officials expect to raise $188 million, or an average of $15.7 million a month, during the fiscal year ending June 30. However, through the first eight months of the fiscal year, monthly collections are averaging about $13.7 million. If that trend continues, the city could be short nearly $24 million in transit funds by midyear.

The city's rail plan anticipated transit tax revenue growing each year. But plunging visitor arrivals, slumping real estate sales and a downturn in construction make it unlikely revenue will be up this year. City officials hope any near-term revenue shortfall will be offset by an economic rebound in future years.

A rebound in tax collections this fiscal year also seems unlikely. Earlier this month, the state Council on Revenues, which generates forecasts used to set the state budget, lowered its projection of state revenues for the fiscal year that ends June 30. The council said revenues would be 5 percent less than the previous year.

The state began collecting a half-percentage point general excise tax surcharge for transit in January 2007. The tax is scheduled to expire in 2022. Overall, that tax has raised nearly $324 million during the first 26 months. That figure, and all figures in this story, do not include the 10 percent the state takes off the top to pay for administering the tax.

During the first eight months of the current fiscal year, the transit tax generated $109 million for the city, which is level with the $109 million raised during the first eight months of the prior fiscal year.

City officials hope to use the tax to raise nearly $4.1 billion, on an inflation-adjusted basis, from 2007 to 2022 to pay for the 20-mile rail system linking East Kapolei to Ala Moana. That, coupled with about $1.4 billion in anticipated federal money, is expected to pay the estimated $5.4 billion in capital costs associated with rail, according to the city's financial plan.

Officials want to begin construction in December, contingent on federal approval, and launch service between 2013 and 2019.