AASHTO T 390-20

The Continuous-Flow Traffic Time-Integrated Method (CTIM) describes the procedures for measuring the influence of road surfaces on highway traffic noise at a specific site. It provides a quantitative measure of the sound pressure level at locations adjacent to a roadway. Measurements capture the sound from existing traffic for all vehicles on all roadway lanes. Measurements also include propagation effects over the roadway pavement and adjacent terrain to the nearby measurement location.

CTIM is to be applied on roadways where measuring single-vehicle pass-by events would be difficult due to continuously flowing, relatively dense traffic (sound levels from single vehicles cannot be properly captured due to contamination from sound from other vehicles).

This standard is intended for use by acoustic professionals. Competency with acoustical measurement, modeling, and analysis techniques is assumed.

This standard was formerly designated as provisional standard TP 99.