Study Details

Study Title: Before-and-after safety study of roadways Where new medians have been added

Authors: Alluri et al.

Publication Date: DEC, 2012

Abstract: The main objective of the study was to evaluate the safety impact of median conversion from two-way left-turn lanes (TWLTLs) to raised medians in Florida. Based on segment length and data availability, 18 locations totaling 17.51 miles were selected for before-and-after analysis. Police reports of all the crashes before and after median conversion were reviewed to correct miscoded crash types and obtain additional detailed crash information. The safety performance of individual locations varied in terms of crash type and crash severity. Overall, the results showed a 30.3 percent reduction in the total crash rate after median conversion. Median conversion was particularly effective in reducing rear-end, angle, left-turn, and right-turn crash rates. Further review of three locations that performed particularly poorly revealed that the majority of crashes that occurred after conversion could not be attributed directly to raised medians.

Study Citation: Alluri, P., Gan, A., Haleem, K., Miranda, S., Echezabal, E., Diaz, A., Ding, S. "Before-and-after safety study of roadways Where new medians have been added." Florida Department of Transportation, (2012).

Related Citations: Allrui, P., A. Gan, and K. Haleem. Safety Impacts of Converting Two-Way Left-Turn Lanes to Raised Medians and Associated Design Concerns. Presented at the 93rd Annual Meeting of the Transportation Research Board, Washington, D.C., (2014).

Study Report: Download the Study Report Document


CMFs Associated With This Study

Category: Access management

Countermeasure: Provide a raised median

CMF CRF(%) Quality Crash Type Crash Severity Roadway Type Area Type
0.742 25.8 3 Stars All O Principal Arterial Other Urban and suburban
0.659 34.1 3 Stars All A,B,C Principal Arterial Other Urban and suburban
0.778 22.2 1 Star All K Principal Arterial Other Urban and suburban
0.66 34 3 Stars All K,A,B,C Principal Arterial Other Urban and suburban
0.697 30.3 3 Stars All All Principal Arterial Other Urban and suburban
0.852 14.8 1 Star Head on O Principal Arterial Other Urban and suburban
0.292 70.8 2 Stars Head on A,B,C Principal Arterial Other Urban and suburban
0 100 2 Stars Head on K Principal Arterial Other Urban and suburban
0.265 73.5 2 Stars Head on K,A,B,C Principal Arterial Other Urban and suburban
0.512 48.8 2 Stars Head on All Principal Arterial Other Urban and suburban
0.896 10.4 3 Stars Rear end O Principal Arterial Other Urban and suburban
0.777 22.3 3 Stars Rear end A,B,C Principal Arterial Other Urban and suburban
0.776 22.4 3 Stars Rear end K,A,B,C Principal Arterial Other Urban and suburban
0.83 17 3 Stars Rear end All Principal Arterial Other Urban and suburban
0.544 45.6 3 Stars Angle O Principal Arterial Other Urban and suburban
0.64 36 3 Stars Angle A,B,C Principal Arterial Other Urban and suburban
0.973 2.7 1 Star Angle K Principal Arterial Other Urban and suburban
0.641 35.9 3 Stars Angle K,A,B,C Principal Arterial Other Urban and suburban
0.595 40.5 3 Stars Angle All Principal Arterial Other Urban and suburban
0.397 60.3 3 Stars Left turn O Principal Arterial Other Urban and suburban
0.295 70.5 3 Stars Left turn A,B,C Principal Arterial Other Urban and suburban
0.243 75.7 2 Stars Left turn K Principal Arterial Other Urban and suburban
0.294 70.6 3 Stars Left turn K,A,B,C Principal Arterial Other Urban and suburban
0.329 67.1 3 Stars Left turn All Principal Arterial Other Urban and suburban
0.571 42.9 2 Stars Right turn O Principal Arterial Other Urban and suburban
0.925 7.5 1 Star Right turn A,B,C Principal Arterial Other Urban and suburban
0.925 7.5 1 Star Right turn K,A,B,C Principal Arterial Other Urban and suburban
0.661 33.9 3 Stars Right turn All Principal Arterial Other Urban and suburban
0.859 14.1 2 Stars Sideswipe O Principal Arterial Other Urban and suburban
0.743 25.7 2 Stars Sideswipe A,B,C Principal Arterial Other Urban and suburban
0.743 25.7 2 Stars Sideswipe K,A,B,C Principal Arterial Other Urban and suburban
0.83 17 3 Stars Sideswipe All Principal Arterial Other Urban and suburban
0.487 51.3 1 Star Vehicle/pedestrian O Principal Arterial Other Urban and suburban
0.661 33.9 2 Stars Vehicle/pedestrian A,B,C Principal Arterial Other Urban and suburban
1.704 -70.4 1 Star Vehicle/pedestrian K Principal Arterial Other Urban and suburban
0.734 26.6 2 Stars Vehicle/pedestrian K,A,B,C Principal Arterial Other Urban and suburban
0.711 28.9 3 Stars Vehicle/pedestrian All Principal Arterial Other Urban and suburban
0.811 18.9 1 Star Vehicle/bicycle O Principal Arterial Other Urban and suburban
1.018 -1.8 2 Stars Vehicle/bicycle A,B,C Principal Arterial Other Urban and suburban
0.487 51.3 1 Star Vehicle/bicycle K Principal Arterial Other Urban and suburban
0.973 2.7 2 Stars Vehicle/bicycle K,A,B,C Principal Arterial Other Urban and suburban
0.955 4.5 2 Stars Vehicle/bicycle All Principal Arterial Other Urban and suburban
1.173 -17.3 2 Stars Rear end All Principal Arterial Other Urban and suburban
0.732 26.8 3 Stars Angle All Principal Arterial Other Urban and suburban
0.664 33.6 3 Stars Left turn All Principal Arterial Other Urban and suburban
0.974 2.6 1 Star Right turn All Principal Arterial Other Urban and suburban
0.597 40.3 2 Stars Sideswipe All Principal Arterial Other Urban and suburban
1.37 -37 1 Star Vehicle/pedestrian All Principal Arterial Other Urban and suburban
0.705 29.5 1 Star Vehicle/bicycle All Principal Arterial Other Urban and suburban
1.028 -2.8 2 Stars Other All Principal Arterial Other Urban and suburban
0.953 4.7 2 Stars All All Principal Arterial Other Urban and suburban
0.941 5.9 2 Stars All O Principal Arterial Other Urban and suburban
0.974 2.6 2 Stars All A,B,C Principal Arterial Other Urban and suburban
0.528 47.2 1 Star All K Principal Arterial Other Urban and suburban
0.965 3.5 2 Stars All K,A,B,C Principal Arterial Other Urban and suburban
0.973 2.7 2 Stars Day time All Principal Arterial Other Urban and suburban
0.998 0.2 1 Star Nighttime All Principal Arterial Other Urban and suburban
0.503 49.7 1 Star Nighttime All Principal Arterial Other Urban and suburban
0.98 2 2 Stars Nighttime All Principal Arterial Other Urban and suburban
0.44 56 2 Stars Nighttime All Principal Arterial Other Urban and suburban
0.377 62.3 2 Stars Other All Principal Arterial Other Urban and suburban
0.477 52.3 2 Stars Head on All Principal Arterial Other Urban and suburban
0.742 25.8 3 Stars Rear end All Principal Arterial Other Urban and suburban
0.558 44.2 3 Stars Angle All Principal Arterial Other Urban and suburban
0.262 73.8 3 Stars Left turn All Principal Arterial Other Urban and suburban
0.529 47.1 2 Stars Right turn All Principal Arterial Other Urban and suburban
0.904 9.6 2 Stars Sideswipe All Principal Arterial Other Urban and suburban
0.596 40.4 2 Stars Vehicle/pedestrian All Principal Arterial Other Urban and suburban
1.006 -0.6 2 Stars Vehicle/bicycle All Principal Arterial Other Urban and suburban
0.827 17.3 3 Stars Other All Principal Arterial Other Urban and suburban
0.628 37.2 3 Stars All All Principal Arterial Other Urban and suburban
0.684 31.6 3 Stars All O Principal Arterial Other Urban and suburban
0.58 42 3 Stars All A,B,C Principal Arterial Other Urban and suburban
0.791 20.9 1 Star All K Principal Arterial Other Urban and suburban
0.582 41.8 3 Stars All K,A,B,C Principal Arterial Other Urban and suburban
0.564 43.6 3 Stars Day time All Principal Arterial Other Urban and suburban
0.512 48.8 2 Stars Nighttime All Principal Arterial Other Urban and suburban
0.416 58.4 2 Stars Nighttime All Principal Arterial Other Urban and suburban
0.859 14.1 3 Stars Nighttime All Principal Arterial Other Urban and suburban
0.931 6.9 2 Stars Nighttime All Principal Arterial Other Urban and suburban
0.465 53.5 2 Stars Other All Principal Arterial Other Urban and suburban
0.275 72.5 2 Stars Head on All Principal Arterial Other Urban and suburban
0.756 24.4 3 Stars Rear end All Principal Arterial Other Urban and suburban
0.462 53.8 2 Stars Angle All Principal Arterial Other Urban and suburban
0.326 67.4 2 Stars Left turn All Principal Arterial Other Urban and suburban
0.943 5.7 1 Star Right turn All Principal Arterial Other Urban and suburban
1.186 -18.6 1 Star Sideswipe All Principal Arterial Other Urban and suburban
1.237 -23.7 1 Star Vehicle/pedestrian All Principal Arterial Other Urban and suburban
1.031 -3.1 1 Star Vehicle/bicycle All Principal Arterial Other Urban and suburban
0.825 17.5 1 Star Other All Principal Arterial Other Urban and suburban
0.682 31.8 3 Stars All All Principal Arterial Other Urban and suburban
0.712 28.8 3 Stars All O Principal Arterial Other Urban and suburban
0.643 35.7 3 Stars All A,B,C Principal Arterial Other Urban and suburban
0.654 34.6 3 Stars All K,A,B,C Principal Arterial Other Urban and suburban
0.639 36.1 3 Stars Day time All Principal Arterial Other Urban and suburban
1.65 -65 1 Star Nighttime All Principal Arterial Other Urban and suburban
0.55 45 1 Star Nighttime All Principal Arterial Other Urban and suburban
0.867 13.3 2 Stars Nighttime All Principal Arterial Other Urban and suburban
0.412 58.8 2 Stars Nighttime All Principal Arterial Other Urban and suburban
0.588 41.2 2 Stars Head on All Principal Arterial Other Urban and suburban
0.881 11.9 3 Stars Rear end All Principal Arterial Other Urban and suburban
0.647 35.3 3 Stars Angle All Principal Arterial Other Urban and suburban
0.348 65.2 3 Stars Left turn All Principal Arterial Other Urban and suburban
0.663 33.7 3 Stars Right turn All Principal Arterial Other Urban and suburban
0.818 18.2 3 Stars Sideswipe All Principal Arterial Other Urban and suburban
0.709 29.1 2 Stars Vehicle/pedestrian All Principal Arterial Other Urban and suburban
0.978 2.2 2 Stars Vehicle/bicycle All Principal Arterial Other Urban and suburban
0.963 3.7 2 Stars Other All Principal Arterial Other Urban and suburban
0.735 26.5 3 Stars All All Principal Arterial Other Urban and suburban
0.783 21.7 3 Stars All O Principal Arterial Other Urban and suburban
0.695 30.5 3 Stars All A,B,C Principal Arterial Other Urban and suburban
0.716 28.4 1 Star All K Principal Arterial Other Urban and suburban
0.695 30.5 3 Stars All K,A,B,C Principal Arterial Other Urban and suburban
0.684 31.6 3 Stars Day time All Principal Arterial Other Urban and suburban
0.625 37.5 3 Stars Nighttime All Principal Arterial Other Urban and suburban
0.444 55.6 2 Stars Nighttime All Principal Arterial Other Urban and suburban
0.928 7.2 2 Stars Nighttime All Principal Arterial Other Urban and suburban
1.181 -18.1 2 Stars Nighttime All Principal Arterial Other Urban and suburban
0.418 58.2 2 Stars Other All Principal Arterial Other Urban and suburban