4.3. Strength and limitations
The noise model (TRANEX) does account for shielding by buildings and diffraction of noise around buildings, but not reflections (Gulliver et al., 2015). The CRTN method on which TRANEX is based includes reflection terms for buildings adjacent to major roads but not elsewhere. The maximum increment in noise levels in CRTN due to reflections is 1.5 dB(A) which applies in full street canyons. In partial street canyons or where buildings along major roads are more dispersed the increment due to reflections will be much lower, in many cases < 1 dB(A). Although we do not account for reflections we, therefore, expect any misclassification to be small, especially if used in an epidemiological context where relative ranking is important, rather than absolute levels of noise.