Why are U-Turns restricted at intersections even when no Restricted Driving Maneuver (RDM) is coded?

Admin Wide Regulations: U-Turns forbidden without RDMs

### Symptoms

U-turns are not permitted at intersections where no Restricted Driving Maneuver (RDM) exists.
Routing results avoid U-turns across an entire city, county, state, or country.
Map data appears inconsistent because an intersection does not contain an explicit U-turn restriction.
Customers expect the default rule of "U-turns allowed unless prohibited" but observe the opposite behavior.
Route validation identifies missing RDM attributes although U-turn restrictions are correctly enforced.

### Answer

This is expected behavior when an Administrative Area has an Admin Wide Regulation that prohibits U-turns by default. In these areas, individual Restricted Driving Maneuver (RDM) restrictions do not need to be coded at every intersection. Instead, the administrative area is configured with ADMIN_WIDE_REGULATIONS = 1, which applies the U-turn restriction across the entire jurisdiction.

### Product / Platform

HERE Map Data (Routing and Navigation Data Model)

### Root Cause

Most regions follow the standard traffic rule that U-turns are allowed unless specifically prohibited. However, some countries, states, counties, or cities apply the opposite rule: U-turns are prohibited at intersections unless explicitly permitted. To efficiently represent these regulations in map data, HERE uses the Admin Wide Regulation attribute rather than creating individual RDM restrictions for every affected intersection.

When an administrative area contains a U-turn prohibition by regulation, the value ADMIN_WIDE_REGULATIONS = 1 is published for that area. Routing engines and related products should interpret this as a jurisdiction-wide restriction.

### Impact

U-turn restrictions may be enforced even when no explicit RDM is present at an intersection.
Data reviewers may incorrectly assume a restriction is missing.
Routing behavior may differ from regions where U-turns are allowed by default.
Quality validation processes must consider Admin Wide Regulations before reporting missing maneuver restrictions.

### Exceptions

Where a U-turn is specifically allowed within an administrative area that generally prohibits U-turns, the exception is represented through Permitted Maneuver Condition coding. In these cases, the permitted maneuver overrides the jurisdiction-wide default restriction.

### Expected Behavior

U-turns are restricted throughout administrative areas configured with ADMIN_WIDE_REGULATIONS = 1.
No individual RDM is required at every intersection affected by the administrative rule.
Explicitly permitted locations are represented using Permitted Maneuver Condition coding.

### Unexpected Behavior

Assuming a missing RDM indicates missing map data when an Admin Wide Regulation already applies.
Treating every intersection without an RDM as unrestricted in jurisdictions where U-turns are prohibited by default.
* Ignoring Permitted Maneuver Condition exceptions in areas governed by Admin Wide Regulations.

### Recommended Actions

1. Check whether the affected country, state, county, or city has an Admin Wide Regulation prohibiting U-turns.
2. Verify if ADMIN_WIDE_REGULATIONS = 1 is published for the relevant administrative area.
3. Review Permitted Maneuver Condition coding before reporting a suspected data issue.
4. Validate routing behavior against local traffic regulations and administrative area rules.

### Keywords / Tags

Admin Wide Regulation, ADMIN_WIDE_REGULATIONS, U-Turn Restriction, U-Turn Prohibited, Restricted Driving Maneuver, RDM, Permitted Maneuver Condition, Routing Behavior, Administrative Area, Map Data, Navigation Rules, Traffic Regulation, Junction Restriction, Route Validation, HERE Map Data

For further details please check the RDF-Reference Manual.