SLIDE 1 Design Meets Reality
Steve Allen
Director Strategic Transportation Investments Division
Zane Pannell
Transportation Project Specialist Strategic Transportation Investments Division
SLIDE 2 Agenda
- Design Element Considerations
- Post Construction Issues
- Crash Statistics
- Proposed Concept
- Lessons Learned
SLIDE 3
Location
SLIDE 4 Alignment
S.R. 109 NB SB
SLIDE 5 13 Controlling Elements of Design
- 1. Design speed
- 2. Lane width
- 3. Shoulder width
- 4. Bridge width
- 5. Horizontal
alignment
- 6. Superelevation
- 7. Vertical alignment
- 8. Grade
- 9. Stopping sight distance
- 10. Cross slope
- 11. Vertical clearance
- 12. Lateral offset to
- bstruction
- 13. Structural capacity
SLIDE 6 13 Controlling Elements of Design
- 1. Design speed
- 2. Lane width
- 3. Shoulder width
- 4. Bridge width
- 5. Horizontal
alignment
- 6. Superelevation
- 7. Vertical alignment
- 8. Grade
- 9. Stopping sight distance
- 10. Cross slope
- 11. Vertical clearance
- 12. Lateral offset to
- bstruction
- 13. Structural capacity
SLIDE 7 Design Speed
- Construction Let: April 2005
- Construction Completed: Summer 2013
- Principal Arterial
- Rolling Terrain
Traffic Data
ADT (2003) 8,550 ADT (2023) 16,850 Directional Distribution 55%‐45% Truck (ADT) 9% Truck (DHV) 6% V (Rural) 60 MPH
RDO1‐TS‐3A
SLIDE 8 13 Controlling Elements of Design
- 1. Design speed
- 2. Lane width
- 3. Shoulder width
- 4. Bridge width
- 5. Horizontal
alignment
- 6. Superelevation
- 7. Vertical alignment
- 8. Grade
- 9. Stopping sight distance
- 10. Cross slope
- 11. Vertical clearance
- 12. Lateral offset to
- bstruction
- 13. Structural capacity
SLIDE 9 Lane Width and Shoulder Width
48’ 24’ 4’ 10’
RDO1‐TS‐3A
SLIDE 10 13 Controlling Elements of Design
- 1. Design speed
- 2. Lane width
- 3. Shoulder width
- 4. Bridge width
- 5. Horizontal
alignment
- 6. Superelevation
- 7. Vertical alignment
- 8. Grade
- 9. Stopping sight distance
- 10. Cross slope
- 11. Vertical clearance
- 12. Lateral offset to
- bstruction
- 13. Structural capacity
SLIDE 11 RDO1‐SE‐3
Horizontal Alignment and Superelevation
1,146’ 2,440’
SLIDE 12 13 Controlling Elements of Design
- 1. Design speed
- 2. Lane width
- 3. Shoulder width
- 4. Bridge width
- 5. Horizontal
alignment
- 6. Superelevation
- 7. Vertical alignment
- 8. Grade
- 9. Stopping sight distance
- 10. Cross slope
- 11. Vertical clearance
- 12. Lateral offset to
- bstruction
- 13. Structural capacity
SLIDE 13
Grade
RDO1‐TS‐3A
SLIDE 14 13 Controlling Elements of Design
- 1. Design speed
- 2. Lane width
- 3. Shoulder width
- 4. Bridge width
- 5. Horizontal
alignment
- 6. Superelevation
- 7. Vertical alignment
- 8. Grade
- 9. Stopping sight distance
- 10. Cross slope
- 11. Vertical clearance
- 12. Lateral offset to
- bstruction
- 13. Structural capacity
SLIDE 15 Stopping Sight Distance
2,449’ 2,449’>570’
RDO1‐TS‐3A
SLIDE 16 Other Design Elements
- Intersection sight distance
- Offset turn lane
- Turn lane storage
SLIDE 17 Other Design Elements
- Intersection sight distance
- Offset turn lane
- Turn lane storage
SLIDE 18 Intersection Sight Distance
RDO1‐SD‐5
2,451’ 2,451’>750’ 2,451>1,330’ Single Unit Truck Intermediate Semi‐Trailers
SLIDE 19 Other Design Elements
- Intersection sight distance
- Offset turn lane
- Turn lane storage
SLIDE 20 Offset Turn Lane Design
TDOT Roadway Design Section 2 Preliminary Design
48’ 96’
SLIDE 21 Other Design Elements
- Intersection sight distance
- Offset turn lane
- Turn lane storage
SLIDE 22 Turn Lane Storage Design
125’ 125’
TDOT Roadway Design Section 2 Preliminary Design
SLIDE 23
So, What’s the Problem
SLIDE 24
SLIDE 25
Direction of Fatal Crash
SLIDE 26 Total Crashes
Construction Completed
SLIDE 27 Injury Severity
Construction Completed
SLIDE 28 Clearance Time
Vi = 0 mph Vf = 22 mph S = 125 ft a = ? a = Vf2‐Vi2 /2S a = 4.12ft/s2 Vi = 0 mph Vf = 22 mph a = 4.12ft/s2 t = ? t= Vf‐Vi /a t = 7.83 sec s = 125 ft V= 60 mph t = 7.83 sec s = ? s = V*t s = 689 ft V= 70 mph t = 7.83 sec s = ? s = V*t s = 804 ft
SLIDE 29 Existing Conflicts
32 Total Conflict Points
SLIDE 30
Conceptual Design
SLIDE 31 Conceptual Conflicts
14 Total Conflict Points
SLIDE 32 Lessons Learned
- Visualize design
- Safety considerations
- Future training
- Check all appropriate design vehicles
SLIDE 33
THANK YOU
Quest?ons & Comments
SLIDE 34
Contact Information
Steve Allen, Director
Strategic Transportation Investment Division Tel: (615) 741‐2208 E‐mail: Steve.Allen@Tn.Gov
Zane H. Pannell, E.I., Trans. Project Specialist
Strategic Transportation Investments Division Tel: (615) 253‐2781 Email: Zane.Pannell@Tn.Gov
SLIDE 35
Conceptual Design
