The problems associated with induction loop failures is addressed through the use of a detailed telephone and literature survey. All Washington State DOT districts, and most of the counties and larger cities are covered along with a random sampling of the major geographic areas of the US.
The rates of failures were somewhat similar throughout the state as well as the country. The major problems associated with loop installation failures were closely related to pavement failures and installation deficiencies. The electronics problems centered around periodic adjustment or alignment procedures which are associated with the type of amplifiers used and with the long term integrity of the loop and lead in wire system. This can be improved by using self aligning amplifiers and by using improved installation techniques.