Collector-express
The successor to the concept of service/frontage roads in urban freeways is the collector-express system, which is designed to handle closely spaced interchange ramps without disrupting through traffic. Unlike service roads, the collector lanes are typically high-speed full controlled-access lanes, conforming to freeway requirements.
The collector lanes may also be known as a collector/distributor road and slip ramps provide access to and from the express/mainline lanes. Frontage roads may feed into and from collector/distributor roads near some interchanges.
Read more about this topic: Frontage Road