Construction related to a “quiet zone,” being developed in downtown San Diego to curb late-night train noise, is now projected to be completed in late spring 2012.

The project was originally scheduled to be finished in early March, but is taking longer due to complexities related to transitioning to new train signaling, timing and safety systems, according to a Dec. 22 statement from the Centre City Development Corp.

The quiet zone was approved by the city in June 2010, and work began earlier this year. Safety enhancements, including new gates, medians, traffic signals and warning lights, are currently being installed and tested at all downtown San Diego grade crossings from Fifth Avenue to Laurel Street.

Officials said the project remains within the budget of $20.9 million approved by the city’s Redevelopment Agency. Once improvements are certified, the railway between Laurel Street and Fifth Avenue will qualify as a “quiet zone” as authorized by the Federal Railroad Administration.

The quiet zone designation exempts that section of the rail corridor from federal regulations requiring that train horns be sounded for 15 to 20 seconds before entering all public grade crossings, except in emergency situations as determined by train engineers. Noise in the downtown waterfront area has spurred complaints from residents, businesses and hotel operators.