Dedicated Left- and 

Right-Turn Lanes at Intersections

Auxiliary turn lanes—either for left turns or right turns—provide physical 

separation between turning traffic that is slowing or stopped and adjacent 

through traffic at approaches to intersections. Turn lanes can be designed to 

provide for deceleration prior to a turn, as well as for storage of vehicles that 

are stopped and waiting for the opportunity to complete a turn.

While turn lanes provide measurable 

safety and operational benefits at 

many types of intersections, they 

are particularly helpful at two-way 

stop-controlled intersections. Crashes 

occurring at these intersections are 

often related to turning maneuvers. 

Since the major route traffic is free 

flowing and typically travels at higher 

speeds, crashes that do occur are 

often severe. The main crash types 

include collisions of vehicles turning 

left across opposing through traffic 

and rear-end collisions of vehicles 

turning left or right with other vehicles 

following closely behind. Turn lanes 

reduce the potential for these types 

of crashes.

Installing left-turn lanes and/or rightturn lanes should be considered 

for the major road approaches 

for improving safety at both threeand four-leg intersections with stop 

control on the minor road, where 

significant turning volumes exist, 

or where there is a history of turnrelated crashes. Pedestrian and 

bicyclist safety and convenience 

should also be considered when 

adding turn lanes at an intersection. 

Specifically, offset left- and right-turn 

lanes will lengthen crossing distances 

for pedestrians.

Offset Turn Lanes

Providing offset of left- and rightturn lanes to increase visibility can 

provide added safety benefits, and 

is preferable in many situations, 

particularly at locations with higher 

speeds, or where free-flow or 

permissive movements are possible. 

At turn lanes with zero or negative 

offset, turning vehicles can block 

sightlines. For left-turn lanes, this 

usually involves opposing left-turning 

vehicles occupying the turn lanes 

at the same time. For right-turn 

lanes, this typically involves rightturning vehicles from the major 

road and vehicles entering the 

intersection from the minor road. 

In both scenarios, adding positive 

offset to turn lanes enhances the 

sight distance to approaching 

vehicles that conflict with the turning 

movement. Offset turn lanes should 

be considered when there is a high 

frequency of these types of conflicts 

in order to reduce the likelihood of a 

severe crash.

FHWA-SA-21-041

Illustration comparing zero offset to positive offset of left- and right-turn lanes. Source: FHWA

Left-Turn Lanes

reduction in total crashes.1

28-48%

Right-Turn Lanes

reduction in total crashes.1

14-26%

Safety Benefits:

Positive Offset 

Left-Turn Lanes

reduction in fatal 

and injury crashes.2

36% 

Zero Offset Positive Offset

1 (CMF ID: 260, 268, 285, 289) Harwood et al. Safety Effectiveness of Intersection 

Left- and Right-Turn Lanes. FHWA-HRD-02-089, (2002).

2 (CMF ID: 6096) Persaud et al. Safety Evaluation of Offset Improvements 

for Left-Turn Lanes. FHWA-HRT-09-035, (2009).

OFFICE OF SAFETY

Proven Safety 

Countermeasures

 Left- and right-turn lanes at a two-way 

stop-controlled intersection. Source: City 

of Greeley, CO 

For more information on this 

and other FHWA Proven Safety 

Countermeasures, please visit 

https://highways.dot.gov/safety/

proven-safety-countermeasures 

and https://www.fhwa.dot.gov/ 

publications/research/safety 

/02103/02103techbrief.pdf.