1. Lane Volume Allocation

2. Reality!
No single lane
all through traffic

3. What to do? Distribute volume among lanes to Lane volume allocation
Identify lane utilization
Determine need for lane adjustment
Estimate critical lane volumes
Lane volume allocation

4. Lane Volume Allocation Rules
All turning movements are placed in exclusive left or right turn lanes, if present
Through traffic is distributed evenly among through lanes
Right turns are equivalent to through movements, if no right turn lanes exist
Shared left and through lane requires special procedure

5. Lane Allocation Example 1

6. Lane Allocation Example 1
250
175
150
180
Left turns in
exclusive turn lanes

7. Lane Allocation Example 1
250
175
150
180
Right turns in
exclusive turn lanes
180
320

8. Lane Allocation Example 1
250
175
150
180
Through in single
through only lanes
650
500
180
320

9. Lane Allocation Example 1
250
175
150
180
585
550
Through and right in
shared lanes
WB ( )/2 = 585
SB ( )/2 = 550
650
500
180
320

10. Lane Allocation Example 2

11. Through Vehicle Equivalents for Left Turns
Opposing Volume Through+Right (vph)
Through Vehicle Equivalents
0-199
1.1
2.0
3.0
4.0
>1000
5.0

12. Lane Allocation Example 2
450
160
200
180
Shared through & left lanes WB
1. Opposing traffic to LT
EB TH+RT = =720
412
413
2. 1 LT =3 TH
3. Total equivalent TH
500+3(75)+100 = 825
4. Per lane 825/2 = 412.5
350

13. Lane Allocation Example 2
450
160
200
180
Shared through & left lanes EB
1. Opposing traffic to LT
WB TH+RT= =600
412
413
350

14. Through Vehicle Equivalents for Left Turns
Opposing Volume Through+Right (vph)
Through Vehicle Equivalents
0-199
1.1
2.0
3.0
4.0
>1000
5.0

15. Lane Allocation Example 2
450
160
200
180
Shared through & left lanes EB
1. Opposing traffic to LT
WBTH+RT= =600
412
413
2. 1 LT =3 TH
3. Total equivalent TH
650+3(120)+70 = 1080
4. Per lane 1080/2 = 540
540
350

16. Lane Allocation Example 2
450
160
200
180
How many TH in shared lane?
412
413 EB
540- 3(120) = 180 vph
540 WB
412- 3(75) = 187 vph
350

17. Example 3 Tophat: What are WB lane volumes?

18. Example 3 Answer

19. Example 3 Tophat: What are EB lane volumes?

20. Example 3 Answer
NOTE: Eastbound right turn volume (250) is greater than through volume. Therefore the right shared lane acts as a de facto right turn lane. All right turn traffic MUST use that lane.

21. Extra Reading Signal Timing Class Notes
See supplemental reading on Course Website section 5.3