Radar trailers are a bit less expensive but also effective only when present. Photo-radar enforcement systems are slightly more effective, but they are expensive to operate since they need staffing. Palo Alto seems to have more stop signs per mile than anywhere else. Speed Control - this group includes three types of control measures and is intended primarily to reduce the speed of cars on the street. As a side effect, installation of speed control measures usually reduces cut-through volume as well.
Modern roundabouts are similar to traffic circles but with added safety features.
Narrowings are called psycho-perception controls which work by making the driver feel that they have less space. They are less effective than other speed control measures which rely on physical forces. As congestion around our neigbhorhood continues to increase, the effect of calming devices on cut-through traffic will continue to errode. Horizontal measures generally create less noise than vertical measures and for that reason might be preferred on streets with large numbers of trucks. Comprehensive traffic calming of German towns in the 1980's resulted in decreaced air pollution.