ISWIM has published a number of brochures in different languages:

Topic / LanguageEngFraEspNedRusChinPort
On the International
Society for WIM		ISWIMISWIMISWIMISWIMISWIMISWIMISWIM
On Applications of
Weigh-In-Motion		Appl.Appl.Appl.Appl.Appl.Appl.Appl.

ISWIM also has developed a document providing a basic, yet a comprehensive introduction to WIM: the ISWIM Guide for Users of Weigh-In-Motion.
To download, click here: Guide for users of WIM