Hardened Centerlines

PurposeSketch Hardencenterlines.png

Reduce vehicle turning speed and increase vehicle yielding to pedestrians.

Description

Hardened centerlines are flexible delineator posts or raised speed humps placed along the yellow centerline at an intersection to block the diagonal path through the intersection and encourage drivers to turn left at a slower speed.

Safety Benefits

  • Slows left-turning vehicles without reducing traffic capacity.
  • Guides vehicles to wider turning angle for safer and more predictable turns.
  • Increases visibility of pedestrians in crosswalk to turning drivers.

  • Studies in Arlington show that centerline hardening decreased the percentage of motorists turning at over 15 mph from 22% to 6%. Before centerline hardening, 38% percent of drivers crossed the centerline, but only 5% did so after installation.

Street Types and Context

Applicable Street Types

Principal and Minor Arterials in Urban and Urban Core contexts. Local Principal and Local Minor streets in all contexts.

Other Location Guidance

  • Hardened centerlines can be installed at intersections or midblock crossing locations.
  • In areas with turn-related crash histories or observed improper yield behaviors.

Primary User Groups

Centerline2b.png

Key Implementation Considerations

The turning paths of the design vehicle must be considered.

  • Can be constructed rapidly and inexpensively using markings and flexible delineators.
  • The turning radius of trucks and buses should be considered when installing hardened centerlines.
  • Roadway maintenance activities like snow removal and street sweeping must also be considered when designing in-street infrastructure.

Expected Crash Reduction

46% for all crashes at raised medians (Bahar et al. 2007).

Cost

$ (highlighted); $$ ; $$$ ; $$$$

Typically, a lower cost treatment.

Timeline

watch icon a quarter of the way full.

Typically, a quick-build treatment

Application in Arlington 

Visit Vision Zero Program Dashboard: Hardened Centerlines to see where this tool has been implemented.

Vision Zero Dashboard

Safety Pilot Project

Arlington County conducted a safety pilot project that added hardened centerlines at five intersections in 2024. This safety treatment reduced vehicle turning speeds and reduced the proportion of cars crossing over the yellow centerline while making a left turn by 33%.

Safety Pilot Project_Hardened centerline.png

References

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