Lars H. Trandem and Kelly Pitera TRADEOFFS BETWEEN A 2+1 LANE ROAD DESIGN AND A NARROW 2+2 LANE ROAD DESIGN Lars H. Trandem and Kelly Pitera

Background AADT: 6 000 – 12 000 Speed Limit: 90 km/h

Background AADT: 12 000 – 20 000 Speed Limit: 100 km/h

Background VS.

Tradeoffs SAFETY OPERATIONS COST

COMPARATIVE L.O.S. ANALYSIS Methods LITERATURE REVIEW COMPARATIVE L.O.S. ANALYSIS CASE STUDY BENEFIT COST ANALYSIS

2+1 Lane Road Design AADT: 8 000 -12 000 Speed limit: 90 km/h

Narrow 2+2 Lane Road Design AADT: 8 000 -12 000 Speed limit: 90 km/h

Traffic Safety Head-on Collisions  Median Barrier Run-off-road Crashes  Lane and Shoulder Width Lack of data

Traffic Safety Head-on Collisions Impact of a median barrier Great success in Sweden with 2+1 lane roads Reduced fatalities by 76% Applicable for both designs Carlsson, A. (2009). Evaluation of 2+1-roads with cable barriers: final report

Traffic Safety Run-off-road Crashes Sufficient Clear Zone Lane and Shoulder Width Studies have shown narrower shoulder and lanes results in higher accident frequencies Bauer, K. M., Harwood, D. W., Hughes, W. E., & Richard, K. R. (2004). Safety Effects of Narrow Lanes and Shoulder-Use Lanes to Increase Capacity of Urban Freeways. Dixon, K., Fitzpatrick, K., & Avelar, R. (2015). Operational and Safety Tradeoffs -- Reducing Freeway Lane and Shoulder Width to Permit an Additional Lane.

Traffic Safety Summary Hard to separate the effects Wider lanes and shoulders are favorable 2+1-road assumed to be safer

Traffic Operations Capacity Level of Service (US) Highway Capacity Manual

Traffic Operations Studies have shown: Capacity of 2+1 lane road is around 1 600 veh/h for one direction Compared to 1900 veh/h for 1+1 lane road A 2+1 lane road does not improve the capacity of a 1+1 lane road But 2+1-roads improve the level of service Multilane highway segments have a capacity of 1 900 – 2 200 veh/h/l Narrow 2+2 lane roads improve capacity and level of service Carlsson, A. (2009). Evaluation of 2+1-roads with cable barriers: final report Transportation Research Board. (2010). Highway Capacity Manual 2010

Level of Service Calculations Traffic Operations Level of Service Calculations Highway Capacity Manual Basic freeway segments (narrow 2+2 road) Adapted two-lane highway method (2+1 road) AADT: 6 000, 12 000 and 20 000 Directional splits: 67/33 and 55/45

Level of Service Calculations Traffic Operations Level of Service Calculations Level of Service Directional split AADT 2+1 Lane road Narrow 2+2 Lane Road 67/33 6 000 C A 12 000 B 20 000 - 55/45 12 000

Norwegian Case Study E16 Kløfta-Kongsvinger Benefit Cost Analysis  Non-monetized  Monetized

Non-monetized Impacts Norwegian Case Study Non-monetized Impacts Landscape Local surroundings and outdoor activities Biodiversity Cultural environment Natural resources

Norwegian Case Study Monetized Impacts Benefit-cost analysis by using the program EFFEKT Alternative 0 (existing situation) Alternative 1 (narrow 2+2 road) Alternative 2 (2+1 road)

Norwegian Case Study Scenario 1 Speed Limit: 90 km/h for both alternatives Road design Accident types that are affected Killed Seriously injured Lightly injured Number of accidents Narrow 2+2-road (Alt. 1) All -75% -45% +25% 2+1-road (Alt. 2) -76% -47% +13%

Norwegian Case Study Scenario 2 Speed Limit: - 90 km/h for narrow 2+2 road (Alt.1) - 85km/h for 2+1 road (Alt.2) Traffic accident effects as in Scenario 1

Norwegian Case Study Scenario 3 Speed Limit: 90 km/h for both alternatives Traffic accident effects assumed equal for both narrow 2+2 road (Alt. 1) and 2+1 road (Alt. 2).

Scenario 1 Scenario 2 Scenario 3   Scenario 1 Scenario 2 Scenario 3 Components Alt. 1 (2+2) Alt. 2 (2+1) Alt.1 (2+2) Alt.2 (2+1) Investment cost [ 1000 NOK] 821 288 (-) 739 159 Change in time cost [1000 NOK] 1 033 775 (+) 873 290 658 631 Change in Accident costs [1000 NOK] 394 703 416 022 416 028 Change in additional miscellaneous costs and benefits [1000 NOK] 174 100 915 160 448 Net present value [1000 NOK] 607 016 651 069 495 942 628 341 Benefit-cost ratio per budget kroner [ ] 1,65 1,82 1,28 1,71

Scenario 1 Scenario 2 Scenario 3   Scenario 1 Scenario 2 Scenario 3 Components Alt. 1 (2+2) Alt. 2 (2+1) Alt.1 (2+2) Alt.2 (2+1) Investment cost [ 1000 NOK] 821 288 (-) 739 159 Change in time cost [1000 NOK] 1 033 775 (+) 873 290 658 631 Change in Accident costs [1000 NOK] 394 703 416 022 416 028 Change in additional miscellaneous costs and benefits [1000 NOK] 174 100 915 160 448 Net present value [1000 NOK] 607 016 651 069 495 942 628 341 Benefit-cost ratio per budget kroner [ ] 1,65 1,82 1,28 1,71

Scenario 1 Scenario 2 Scenario 3   Scenario 1 Scenario 2 Scenario 3 Components Alt. 1 (2+2) Alt. 2 (2+1) Alt.1 (2+2) Alt.2 (2+1) Investment cost [ 1000 NOK] 821 288 (-) 739 159 Change in time cost [1000 NOK] 1 033 775 (+) 873 290 658 631 Change in Accident costs [1000 NOK] 394 703 416 022 416 028 Change in additional miscellaneous costs and benefits [1000 NOK] 174 100 915 160 448 Net present value [1000 NOK] 607 016 651 069 495 942 628 341 Benefit-cost ratio per budget kroner [ ] 1,65 1,82 1,28 1,71

Case Study Monetized Impacts Conclusion Case Study Monetized Impacts Which design is most economical beneficial? - It depends……

Conclusion Traffic Safety Both designs improve the traffic safety Assuming a slight advantage to the 2+1 lane road - wider lanes and shoulders - assumed lower mean speed

Conclusion Traffic Operations 2+1 lane road - No increase in capacity - Improved level of service Narrow 2+2 lane road - Increase in capacity - Improved level of service

Final Conclusions 2+1 with certain volume conditions Need for more data