CONTRAFLOW-LEFT INTERCHANGE
I-69 AT THIRD STREET (INDIANA 48)
IN BLOOMINGTON INDIANA

WOULD IT WORK?         CAN IT BE BUILT?

3rd St CDL

Third Street at Interstate 69 and Indiana 37

I-69 and IN-37 run north and south (vertical in the photo). Third Street runs east and west. The orange lines are the small barriers needed to separate traffic moving in opposite directions.

The Plan

The basic plan is to rearrange the lanes in this tight urban diamond interchange (TUDI) to make the left turn lanes pass to the left of each other. Special overhead signs direct traffic to the proper lanes. The following diagram shows the lane uses intended:

                                             
        cnw nrt nrt nlf               sth sth sth cne        
cnw     eth non non non non cne           cnw non non non non ert   ert  
  eth   eth non non non non non eth   eth   eth non non non non non eth   eth  
  eth   eth non non non non non eth   eth   eth non non non non non eth   eth  
         
h0z h0z cnw wth non non non non non wlf   wlf   wlf non non non non h0z h0z h0z h0z cnw
cnw wlf lne wth non non non non non wlf non wlf non wlf non non non non h0z h0z cnw elf cse
               
lne wlf cse h0z h0z non non non non elf   elf   elf non non non non non eth cse h0z h0z
           
  wth   wth non non non non non wth   wth   wth non non non non non wth   wth  
  wth   wth non non non non non wth   wth   wth non non non non non wth   wth  
  wrt   wrt non non non non cse           cse non non non non wth     csw
        csw nth nth nth               slf sfl srt cse        
                                             

ADVANTAGES:

  1. Allows storage of more left turns entering Indiana 37
  2. Left turns from 3rd Street don't cross each other's paths
  3. Allows a longer cycle length for the traffic signals
  4. Fits in the current space
  5. Minimal costs to convert interchange
  6. Can use a single signal controller with double clearance functions for both intersections
  7. Can use lead-lead, lead-lag, or lag-lag signal phasing
  8. Can handle discharge of long queues from one direction on 3rd St

DISADVANTAGES:

  1. Left turn traffic can back up, blocking the other intersection
  2. Will not help the jams at adjacent intersections
  3. Possible confusion because left turns pass between lanes going the other way
  4. Does not improve off-ramp left turns
  5. Needs special signs
  6. Requires some painted lines to always be present
  7. Cannot use permissive left turn phasing