They would need to install some security barricades (see: http://www.deltascientific.com/hs_highsecbarricades.htm ) if they wanted to stop a suspicious vehicle. There are similar devices on I-93 on the approach to the Hoover Dam. However, the tunnels and bridges the NYPD are considering the sensors and cameras are much wider than the one I mentioned. Who knows if these barricades would be considered in their plans.