Transportation advocates are largely convinced that massive investment in the area's infrastructure will be essential to cope with increasing demand and aging in-place facilities.  But even when transit agencies try to move ahead with improvements, they often run into opposition from communities which fear adverse effects from the projects.  Consider the Long Island Rail Road's plan to add a third track to its busy main line from Floral Park -- where the existing four-track line ends -- to Hicksville, where the line divides into two two-track branches. The ten-mile bottleneck has been in place for a century, yet in that period Long Island has changed from a sleepy agricultural area to a burgeoning bedroom community in which tens of thousands of commuters depend on the railroad to get to work. Improvements allowing use of the two tracks in either direction have helped, but demand continues to outpace capacity; thus, the plan for a third track to handle what has become 107,000 passengers each weekday on the line. But according to reporting by Joseph De Avila in the Wall Street Journal (Feb. 14), towns along the line are reacting negatively  to the proposal, and the years of disruption that the project would entail. Mayors of online communities Garden City and Mineola argue that the demand can be satisfied without adding a third track, and residents say the benefits won't be worth the "headaches that construction would cause." And Floral Park's mayor questions whether the estimated three-to-four-year construction period is realistic.  On the other hand, businesses, construction companies, and real-estate interests, predictably, endorse the plan.