Vertical Delineation, 2014

Vertical delineators are intended to warn drivers of an approaching curve while providing them with a better appreciation of the sharpness of a curve. Drivers can then select an appropriate speed before entering the curve. Delineation can also provide continuous tracking information once drivers are within the curve to help position their vehicles within the travel lane while traversing the curve. The most common type of vertical delineation is post mounted delineators (PMDs). These devices are usually flexible or rigid posts with some amount of reflective surface mounted along the roadside to provide additional delineation. Another treatment that has been used is to provide additional delineation on chevron posts.

Vertical Clearance Restrictions on Primary Roads and Primary Road Extensions: Standard U.S. Measurements [Vertical Clearance Log], May 1, 2015

The Vertical Clearance Log is prepared for the purpose of providing vertical clearance restrictions by route on the primary road system. This report is used by the Iowa Department of Transportation’s Motor Carrier Services to route oversize vehicles around structures with vertical restrictions too low for the cargo height. The source of the data is the Geographic Information Management System (GIMS) that is managed by the Office of Research & Analytics in the Performance & Technology Division. The data is collected by inspection crews and through the use of LiDAR technology to reflect changes to structures on the primary road system. This log is produced annually.