Traffic is controlled by several different things in Trainz.
Firstly, it must be enabled in the Environment Tools, which I presume you have done.
Secondly, the roads used in the layout must be configured to carry traffic (not all roads are configured for traffic and therefore will not have any regardless of the Environment Tools setting)
Thirdly, the region set in the Edit Route option must have at least one road vehicle specified. Not all regions include road traffic. It is possible that S&C 1960 does not have any road vehicles - try a different region and see what happens. When you change the region you will also change other features of the route.
