1. Optimizing The Evaluation of The Life Cycle Impacts of Intersection Control Type Selection
Presented by Joy Davis, ITRE
TRB Planning Applications Conference
May 15, 2017

2. Problem
Lack of standard process for conversion of Two-Way Stop Controlled intersection
Roundabout?
All-Way Stop?
= Possible inefficient allocation
of funds + ongoing safety & delay problems
Signal?

3. Goals
Provide guidance for conversions of two-way stop controlled (TWSC) intersections to other types to enhance the effective allocation of public funds:
Create an analytic model that accounts for variables that impact the life cycle costs of conversions
Develop a user-friendly planning-level tool that requires minimal time & effort
Use Life Cycle Cost Analysis (LCCA) framework to compares the monetized outcomes of alternatives

4. Scope Four-Way TWSC Intersection Conversions To: Approach All-Way Stop
Signal
Roundabout
Approach
Outcomes calculated using HCM, HSM, MUTCD, NCHRP, and other peer-reviewed methods
Monetized using standard LCCA methods

5. Variables Construction & Maintenance
Capital funds needed for conversion (including ROW and PE)
Three cost tiers based on 5 years of NCDOT SPOT projects
Cost of annual upkeep + revisions at end of service life
User Delay
Idling (based on fuel prices)
Value of travel time
Control delay
Safety
Last 3-5 years if crash data for TWSC intersection
KABCO costs
Crash Reduction Factors for post-conversion outcomes

6. Monetization
TWSC is considered “0” starting point – only post-conversion outcomes counted
3% discount rate used to project values into the future
𝑃𝑉= 𝐴𝐵 𝑦 𝑓 (1+𝑟) 𝑦 𝑓− 𝑦 𝑖
Final outputs are Net Present Values (benefits minus costs)
Alternative with highest NPV considered the best option

7. One-Stop Shop Takes 10-15 minutes Minimal user inputs in one platform
Many standards/defaults available
Delay and other variables calculated in-tool
Easily updated, flexible default values
GUI-heavy and simple interface

8. Step 1 – Current Site Volume and configuration details
Some drop-downs, some manual inputs
Prepped for report format

9. Step 2 - Traffic Demand Three data options
Hourly Counts most time-consuming
AADT least precise

10. Step 2 - Traffic Demand
Hourly Counts - 13 or More Hours of Turning Movement Counts

11. Step 2 - Traffic Demand
Peak Hour Count - 12 or Less Hours of Turning Movement Counts

12. Step 2 - Traffic Demand
AADT - No or Few Turning Movement Counts Available

13. Step 3 - Crash Data 3-5 Years of data required KABCO breakdown needed
Crash costs in defaults

14. Steps 4, 5, & 6 - Configurations
Construction costs and conversion configurations
Planning ahead saves time
Key to calculating long-term outcomes

15. Step 4 - Roundabout Configuration

16. Step 5 - AWSC Configuration

17. Step 6 - Signal Configuration

18. Output Summary

19. Printable Report

20. Java Tool Designed for national use Faster and more precise
Available for feedback in Fall 2017
Contact Joy Davis for early access

21. Thank you! Question? Comments? Research Team:
Joy Davis,  Chris Cunningham, Behzad Aghdashi, Daniel Findley, and Sangkey Kim