The South Dakota Department of Transportation will be placing Centerline Rumble Stripes (CLRS) on stretches of state highways with high traffic numbers. CLRS are a proven countermeasure to reduce the risk of cross centerline crashes such as head-on and side-swipe collision. Although these types of crashes represent a low number of overall crashes in South Dakota, they represent a significant number of severe crashes due to the high speed differential. CLRS are a low cost safety improvement that have been shown to reduce cross centerline crashes by 50 percent.

Centerline Rumble Stripe Facts

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• Centerline Rumble Stripes (CLRS) are grooved patterns in the pavement placed on the centerline that provide both an audible warning and a physical vibration to alert drivers that they are leaving the driving lane.

• CLRS are a proven low-cost safety improvement to reduce target crash types. Target crashes for CLRS are head-on, sideswipe opposing, and runoff-road left – statewide there were 263 fatal and serious injury crashes of these types on rural two-lane state highways between 2021 and 2025. This accounts for 17% of all fatal and serious injury crashes on state highways.

• The 2024 South Dakota Strategic Highway Safety Plan (SHSP) identifies CLRS as a priority safety strategy for reducing head-on vehicle collision with a 60% reduction of this crash type in South Dakota.

• SDDOT implemented CLRS guidelines in 2016 to reduce lane departure crashes systematically and proactively.

• The SDDOT started initiating standalone shoulder rumble strip projects in 2010. Since these installations, SDDOT has seen a 20% reduction in fatal and serious injury run-off-road.

• The guidelines recommend that CLRS be placed on rural, undivided roadways with daily traffic greater than 500 vehicles.

• Lane departure crashes occur on all types of roadways; however, there are some common factors that were used to determine roads covered in the guidelines:

  • Driver related - Young drivers, fatigued and drowsy drivers, distracted driving, and higher speeds.

  • Road and environmental related - Two-lane, undivided roads, rural, high speed roads, high traffic volumes, horizontal and vertical curves.

• Noise Concerns

  • One of the designed intents of CLRS is to get the driver’s attention through noise; this can be disturbing to residences near CLRS.

  • SDDOT CLRS guidelines allow flexibility in gapping rumbles near residences.

  • SDDOT has developed its own sinusoidal (mumble) strip designs that have significant reductions in external nuisance noise.

To learn more about CLRS in South Dakota:
Centerline Rumble Stripe Fact Sheet

Centerline rumble stripe Video

These interchanges have been shown to increase capacity and safety, decrease congestion and minimize the cost of new infrastructure.

Benefits & Advantages:

• Safety – Reduces the number of ways vehicles can collide by almost half (14 compared to 26 for a conventional diamond interchange).
• Greater capacity and efficiency – Accommodates more traffic than conventional designs. Drivers make free-flow right and left turns on to the major freeway.
• Easy navigation – Guides drivers with overhead signs, pavement marking, and traffic signals.
• Meets the needs of all road users – Accommodates large trucks, pedestrians and bicyclists.

Navigating A DDI:

• Drivers follow the signs, signals and pavement markings to cross through the intersection at the first set of traffic lights. Traffic appears as if on a one-way street.
• All left turns onto the freeway are free flow, meaning vehicles do not have to stop to access the ramp.
• Vehicles going straight simply proceed through a second set of traffic lights.
• Pedestrians travel on designated walkways and cross only at the crosswalks.
• Bicyclists may choose to use the bike lane or pedestrian walkways and crosswalks.
  

Cost-Effectiveness:

• For improvement projects, a Diverging Diamond interchange often uses the existing bridge structure and the existing right of way, which eliminates the cost of building new structures and purchasing additional right of way. 
• Because many of the existing interchange features remain intact, the Diverging Diamond interchange is often built in less time than it would take to build a new interchange and with significantly less impact to motorists. 
• A Diverging Diamond interchange usually requires the purchase of less right of way and the construction of fewer lanes and bridge structures than traditional interchange types.