Retting, R.A., and Farmer, C.M. Use of pavement markings to reduce excessive traffic speeds on hazardous curves. Paper presented at the Transportation Research Board 77th Annual Meeting, January 1998.
These programs are intended to complement and support current methods of speed control which emphasize speed limits, enforcement, and public information and education. Separately, traffic calming and enforcement tend to be most appropriate for different kinds of situations. The approaches can work together, however, with an integrated approach combining PI&E, enforcement, and engineering as appropriate to make it more certain that the desired effects will be achieved. NHTSA, with its long history of support for pedestrian safety and for speed control, should be a critical supporter of efforts to bring traffic calming and other such tools into the battle.
At the other end are approaches specifically intended to increase safety for pedestrians and other non-motorists and, in many areas, to improve the ambience for residents. These approaches usually include permanent engineering changes to roadways which require slower traffic speeds. The changes can be dramatic and very significantly reduce pedestrian and vehicle crashes. Perhaps more than enforcement does, though, they depend on public understanding, planning involvement, and approval for their success.
N is used almost everywhere in the world. M is used initially when departing oceanic airspace, such as airports in Iceland, Greenland, Bermuda, and the Bahamas. The flight plan is changed to Mach as the cruise speed over the first waypoint in Oceanic airspace and back to N when leaving oceanic airspace.
US Transportation Secretary Ray LaHood - big plans for US High Speed Rail
"New high-speed trains will link 80 percent of Americans within 25 years, at a cost of about $500 billion" - 8/12/10