Detours – Selection and Design

1. Detours – Selection and Design Highways & Engineering Conference March 2, 2006

4. Presenters: • Paul Ferry, Highways Engineer • Lesly Tribelhorn, Highways Design Engineer

5. Objectives • Know which types of detours are appropriate • Apply proper design criteria • Consider safety and costs • Think about environmental, other site constraints • Know where to look for information

6. Types of Detours

7. Types of Detours • Detour traffic onto an existing route • Temporary detour • Median crossovers (divided highways) • Lane closures • Part-width construction

8. Interstate/Freeway

9. Interstate/Freeway • Median crossovers – design considerations • Guardrail • Bridge widths • Interchange proximity and access • Review distance between crossovers • Location (topography, geometrics, distance between) • Drainage • Future projects

10. Interstate/Freeway • Median crossovers – safety • Ingress/egress controlled • Interstate standards met • Two-way traffic • Cross over of traffic • No passing

11. Interstate/Freeway • Median crossovers – cost considerations • Construct & remove crossover • Traffic control (length, maintenance) • Guardrail revisions • Median crossovers – site constraints • Topography considerations for crossover location • No environmental • No R/W

40. Interstate/Freeway • Lane closure – design considerations • Bridge widths • Temporary barrier rail • Length of area to be protected • Barrier deflection • Taper rates • End treatment

41. Interstate/Freeway • Lane closure – safety • Directional traffic separated • Interstate standards met • Access controlled • Excavation located next to travel lane • Bridge work – extended duration • No passing

42. Interstate/Freeway • Lane closure – cost considerations • Traffic control • Lane closure – site constraints • Interchange locations

43. Interstate/Freeway • Temporary detours – design considerations • Usually for culvert replacement in high fill • May need temporary widening, barrier rail • Jack and bore instead (≤48” diameter)? • Need temporary access control fence? • Proximity of interchanges

44. Interstate/Freeway • Temporary detours – safety • Short length • Driver expectations violated • Temporary detours – cost considerations • Construction & removal of detour • Traffic control minimized

45. Interstate/Freeway • Temporary detours – site constraints • Environmental involvement possible • R/W, access fence possible

46. Interstate/Freeway • Detour traffic onto an existing route • Bridge widths, structural capacity, clearance • Road surfacing and structure • Roadway width • Safety issues (mixing traffic, accesses, standards) • Clear zone • Length and duration of detour • Costs - traffic control and surfacing improvement

47. Interstate/Freeway

48. Two-lane rural routes

49. Two-lane rural routes • Detour onto an existing route - design • Cost of temporary detour excessive? • Bridge widths and capacity • Adequate clearance • Roadway widths and structural capacity • Clear zone • Work with construction and maintenance

50. Two-lane rural routes • Detour onto an existing route • Safety depends on route selected • Costs minimal – traffic control, route maintenance • Site constraints should be minimal