Displaced Left-Turn (DLT)
INT-DLT-14 Displaced Left-Turn (DLT)
Typical at: Suburban Compact Urban
Rural is an unlikely pairing. Core is an edge case.
Working assessment: this pattern's status reflects a preliminary Commonway System judgment call, pending final review.
#Design notes
This design resolves the same unprotected-left-turn conflict as Median U-Turn and Restricted Crossing U-Turn, but through signalized displacement rather than a median crossover, and at high-volume urban or suburban intersections rather than the higher-speed rural and suburban divided highways those two patterns typically suit. It's a faster, lower-cost alternative to a grade-separated interchange where volume is high enough that conventional protected left-turn phasing creates severe delay. The additional right-of-way this pattern requires upstream of the main intersection, and its higher construction cost relative to Median U-Turn or Restricted Crossing U-Turn, keep it Situational rather than broadly Recommended.
#Related patterns
Median U-Turn (INT-MUT-12), Restricted Crossing U-Turn (INT-RCU-13) (the two lower-cost alternatives addressing the same underlying unprotected-left-turn problem in a different speed and volume context), Grade-Separated Interchange (INT-GSI-10) (the higher-cost alternative this pattern is often chosen instead of)
#Getting there: Retrofit path options
Displaced Left-Turn (DLT) retrofit (RFT-INT-04) reroutes an existing conventional intersection's left-turn movement to this geometry.
#References
- Evidence-based "Unconventional Arterial Intersection Designs under Connected and Automated Vehicle Environment: A Survey," on Displaced Left-turn Intersection design and cost tradeoffs relative to grade-separated interchanges.
- Legal / regulatory U.S. Patent 7,135,989, "Parallel flow vehicle turn system for traffic intersections," on displaced left-turn design and right-of-way considerations.