Today, the state parkways are for the most part equivalent to expressways and freeways built in other parts of the country, except for a few oddities. First, because many of these roads were either designed before civil engineers had experience building roads for automobile use or widened in response to increasing traffic, many New York parkways lack shoulders. Second, because designers focused more on making routes scenic rather than efficient, the parkways are meandering, often built to follow a river, and so contain many turns. Finally, because most use low, decorative stone-arch overpasses that would trap trucks, commercial vehicles, trucks and tractor trailers are banned from parkways. In Manhattan, this has led to nearly all trucks being forced onto local streets as the island has only one short Interstate (the Trans-Manhattan Expressway) passing through Washington Heights, a neighborhood in Upper Manhattan.