A single-article Special Town Meeting earlier this month approved the purchase of 5 acres on Bedford Road for $590,000, in a vote  far more than the required two-thirds majority. If the measure wins a simple majority in a special town election Tuesday, the purchase would be financed by a $190,000 transfer from free cash and $400,000 of debt. The town plans to use a portion of the land for housing for developmentally disabled adults, qualifying it for Chapter 40B classification, with other parts likely to be devoted to public trails and recreation, as are the two neighboring parcels. If approved in the election, construction on the property is expected to begin in 2014.