1. NC-54 at Farrington as Offset Intersection
April 6, 2017
NC-54 at Farrington as Offset Intersection
Joe Hummer, Mobility and Safety
Nick Lineberger, Congestion Management

2. Existing Configuration

3. Existing Configuration

4. Widening Configuration

5. Offset Intersections Separate conflict points
Give driver time to react
Fewer signal phases on main street
Opportunity to implement synchronized street or continuous flow intersection (CFI) features
Especially right then left offset
More pedestrian crossing opportunities
Some academic literature

6. Reasons to Believe Offset Intersection Might Work at NC-54 and Farrington
Falconbridge parallel to Farrington
Farmington Drive as connector
950 feet between Farrington and Falconbridge should be enough room
Apparent space along Falconbridge and NC-54
Could employ synchronized street features
Best progression of any at-grade intersection
Could employ continuous flow intersection (CFI) features
Highest capacity of any at-grade intersection

7. Offset Intersection Concept at NC-54 and Farrington
Access
Access
Farrington
Access
Falconbridge
Farmington Drive

8. Rerouted SB Left Turn NC-54 Access Access Farrington Access
Falconbridge
Farmington Drive

9. Rerouted SB Through NC-54 Access Access Farrington Access Falconbridge
Farmington Drive

10. Rerouted NB Left NC-54 Access Access Farrington Access Falconbridge
Farmington Drive

11. Rerouted NB Through NC-54 Access Access Farrington Access Falconbridge
Farmington Drive

12. Offset Intersection – Full Movement Signal at Falconbridge

13. Offset Intersection Concept with CFI
New
access
Access
Access
Farrington
Access
Falconbridge
Farmington Drive

14. CFI Geometry at NC-54 and Falconbridge

15. CFI Geometry on Falclonbridge

16. Offset Intersection – CFI Concept

17. Downsides of Offset Plans
Cost
Too costly to do quickly?
Impacts on Falconbridge and Farmington Drive
Wayfinding
No CFI open in NC yet
Signal progression
Full signals at Falconbridge and I-40 EB ramps about feet apart
About 37 percent efficiency with current speed and cycle length

18. Superstreet Concept at Falconbridge
Maintain Farrington as Left-In/Right-Out
Provide better progression along NC-54
Tight spacing for U-turns between Falconbridge and Farrington

19. Superstreet Concept at NC-54 and Falconbridge
Access
Access
Farrington
Access
Falconbridge
Farmington Drive

20. Offset Intersection – Superstreet at Falconbridge

21. Simulation Result Summary Travel time in hours
Configuration
AM peak
PM peak
Existing
1650
1630
Widening
1090
1380
Offset with conventional Falcolnbridge
490
690
Offset with CFI Falcolnbridge
550
540
Superstreet
880
890

22. Conclusions
Offset intersection concept moves queues away from I-40 ramps
Standard full movement signal at Falconbridge provides LOS D or better at all intersections
CFI concept at Falconbridge provides further improvement during PM peak
Worth additional impacts?

23. Conclusions
Offset intersection concept could help on NC-54 at Farrington
Worth further exploration
Need costs and impacts
Don’t forget median u-turn as well
Temporary help or permanent solution?
Offset concept can help other places
Maximize capacity while impacting only chosen quadrants
Take best advantage of synchronized street and CFI features

24. Thank You. Joe Hummer, jehummer@ncdot. gov, 919-814-5102
Thank You! Joe Hummer, Nick Lineberger,