The National Roadway Traffic Noise Exposure Model (NRTNEM) is comprised of a collection of on-line datasets, some containing programs and others containing data. This manual describes the NRTNEM system as it existed on the NCC (EPA's National Computer Center) in December 1981, under user ID EPADYN. NRTNEM actually consists of two models: The General Adverse Response Model ('GAR'), and the Single Event Model ('SEM'). Only one of them can be executed by a job at a time. The User's Manual describes job submission procedures. This manual describes the NRTNEM system in more detail so as to facilitate program maintenance. This manual is organized from two points of view: present first those items the user first comes into contact with, and go from the general to the specific. Accordingly, the general properties of files and datasets are described first, and the coding details are last.