Instead of using the standard MVC routing approach, I needed full control over route construction. In particular, I need to be able to supply routing names for a group of related scenarios.

    name: "BusinessArea",
    url: "BusinessArea/{businessArea}/{action}",
    defaults: new { controller = "BusinessArea", action = "Index" },
    constraints: new { businessArea = @"\d+" });

Gets replaced with:

private static void ExplicitRouteConstruction(RouteCollection routes)
    var defaults = new RouteValueDictionary { { "controller", "BusinessArea" }, { "action", "Index" } };
    var constraints = new RouteValueDictionary { { "businessArea", @"\d+" } };</code>

    var route = new Route(
        new MvcRouteHandler());

    routes.Add("BusinessArea", route);

Later, I can modify this example to supply the default BusinessArea value.