Decision Support Framework and Parameters for Dynamic Part-Time Shoulder Use: Considerations for Opening Freeway Shoulders for Travel as a Traffic Management Strategy

Appendix D. Generalized Thresholds for Opening Shoulder

The tables in this appendix present the number of minutes until capacity is reached on a freeway. When this duration begins to approach the duration of the sweep time, an operator should consider opening a shoulder. More specific information on these tables follows.

These tables were developed in this project to provide simple, off-the-shelf decision parameter values for agencies operating D-PTSU, particularly newer agencies without established practices and experience. They were developed using methods I and III as described in chapter 4. A user begins by identifying the capacity of the bottleneck being relieved with PTSU, and chooses the appropriate table. Identifying the capacity of a bottleneck is discussed in chapter 4. Once the appropriate table is selected, a user chooses the current volume per lane from the left column and the change in volume in the past five minutes from the top portion of the table. Both volume values are presented in terms of vehicles per hour, and the current volume could be measured over a shorter period of time (say the previous 15 or 30 minutes) to be more reflective of current traffic conditions. Once the two volume values are selected, the number in the body of the table indicates the minutes until capacity is reached. In this appendix, times of less than 20 minutes are red and times of 20-30 minutes are green. This example illustrates a facility with 20-minute sweep time. An operator should consider initiating shoulder-opening activities if the table returns a green or red number. A red number indicates the freeway will reach capacity before the shoulder is opened.

The methods described in chapter 4 are ultimately the most reliable for forming decisions of when to open and close the shoulder, but it is recognized that use of these tables is less resource-intensive.

Table 13. Minutes until Capacity is reached when per lane capacity is 2,100 veh/h/ln.
Bottleneck Per Lane Capacity Minutes until Capacity Is Reached
Increase in Hourly Volume Rate In Past 5 Minutes
2,100 10 20 30 40 50 60 70 80 90 100
Current Volume (veh/h/ln)
0 210 105 70 53 42 35 *30 *27 *24 *21
100 200 100 67 50 40 34 *29 *25 *23 *20
200 190 95 64 48 38 32 *28 *24 *22 *†19
300 180 90 60 45 36 30 *26 *23 *20 *†18
400 170 85 57 43 34 *29 *25 *22 *†19 *†17
500 160 80 54 40 32 *27 *23 *20 *†18 *†16
600 150 75 50 38 *30 *25 *22 *†19 *†17 *†15
700 140 70 47 35 *28 *24 *20 *†18 *†16 *†14
800 130 65 44 33 *26 *22 *†19 *†17 *†15 *†13
900 120 60 40 *30 *24 *20 *†18 *†15 *†14 *†12
1,000 110 55 37 *28 *22 *†19 *†16 *†14 *†13 *†11
1,100 100 50 34 *25 *20 *†17 *†15 *†13 *†12 *†10
1,200 90 45 *30 *23 *†18 *†15 *†13 *†12 *†10 *†9
1,300 80 40 *27 *20 *†16 *†14 *†12 *†10 *†9 *†8
1,400 70 35 *24 *†18 *†14 *†12 *†10 *†9 *†8 *†7
1,500 60 *30 *20 *†15 *†12 *†10 *†9 *†8 *†7 *†6
1,600 50 *25 *†17 *†13 *†10 *†9 *†8 *†7 *†6 *†5
1,700 40 *20 *†14 *†10 *†8 *†7 *†6 *†5 *†5 *†4
1,800 *30 *†15 *†10 *†8 *†6 *†5 *†5 *†4 *†4 *†3
1,900 *20 *†10 *†7 *†5 *†4 *†4 *†3 *†3 *†3 *†2
2,000 *†10 *†5 *†4 *†3 *†2 *†2 *†2 *†2 *†2 *†1
2,100 *†0 *†0 *†0 *†0 *†0 *†0 *†0 *†0 *†0 *†0
2,200 -- -- -- -- -- -- -- -- -- --

veh/h/ln = vehicles per hour per lane.
-- = not applicable.
* Operator should consider initiating shoulder-opening activities.
† The freeway will reach capacity before the shoulder is opened.

Table 14. Minutes until Capacity is reached when per lane capacity is 2,000 veh/h/ln.
Bottleneck Per Lane Capacity Minutes until Capacity Is Reached
Increase in Hourly Volume Rate In Past 5 Minutes
2,000 10 20 30 40 50 60 70 80 90 100
Current Volume (veh/h/ln)
0 200 100 67 50 40 34 *29 *25 *23 *20
100 190 95 64 48 38 32 *28 *24 *22 *†19
200 180 90 60 45 36 30 *26 *23 *20 *†18
300 170 85 57 43 34 *29 *25 *22 *†19 *†17
400 160 80 54 40 32 *27 *23 *20 *†18 *†16
500 150 75 50 38 *30 *25 *22 *†19 *†17 *†15
600 140 70 47 35 *28 *24 *20 *†18 *†16 *†14
700 130 65 44 33 *26 *22 *†19 *†17 *†15 *†13
800 120 60 40 *30 *24 *20 *†18 *†15 *†14 *†12
900 110 55 37 *28 *22 *†19 *†16 *†14 *†13 *†11
1,000 100 50 34 *25 *20 *†17 *†15 *†13 *†12 *†10
1,100 90 45 *30 *23 *†18 *†15 *†13 *†12 *†10 *†9
1,200 80 40 *27 *20 *†16 *†14 *†12 *†10 *†9 *†8
1,300 70 35 *24 *†18 *†14 *†12 *†10 *†9 *†8 *†7
1,400 60 *30 *20 *†15 *†12 *†10 *†9 *†8 *†7 *†6
1,500 50 *25 *†17 *†13 *†10 *†9 *†8 *†7 *†6 *†5
1,600 40 *20 *†14 *†10 *†8 *†7 *†6 *†5 *†5 *†4
1,700 30 *†15 *†10 *†8 *†6 *†5 *†5 *†4 *†4 *†3
1,800 * *†10 *†7 *†5 *†4 *†4 *†3 *†3 *†3 *†2
1,900 *†10 *†5 *†4 *†3 *†2 *†2 *†2 *†2 *†2 *†1
2,000 *†0 *†0 *†0 *†0 *†0 *†0 *†0 *†0 *†0 *†0
2,100 -- -- -- -- -- -- -- -- -- --
2,200 -- -- -- -- -- -- -- -- -- --

veh/h/ln = vehicles per hour per lane.
-- = not applicable.
* Operator should consider initiating shoulder-opening activities.
† The freeway will reach capacity before the shoulder is opened.

Table 15. Minutes until Capacity is reached when per lane capacity is 1,900 veh/h/ln.
Bottleneck Per Lane Capacity Minutes until Capacity Is Reached
Increase in Hourly Volume Rate In Past 5 Minutes
1,900 10 20 30 40 50 60 70 80 90 100
Current Volume (veh/h/ln)
0 190 95 64 48 38 32 *28 *24 *22 *†19
100 180 90 60 45 36 30 *26 *23 *20 *†18
200 170 85 57 43 34 *29 *25 *22 *†19 *†17
300 160 80 54 40 32 *27 *23 *20 *†18 *†16
400 150 75 50 38 *30 *25 *22 *†19 *†17 *†15
500 140 70 47 35 *28 *24 *20 *†18 *†16 *†14
600 130 65 44 33 *26 *22 *†19 *†17 *†15 *†13
700 120 60 40 *30 *24 *20 *†18 *†15 *†14 *†12
800 110 55 37 *28 *22 *†19 *†16 *†14 *†13 *†11
900 100 50 34 *25 *20 *†17 *†15 *†13 *†12 *†10
1,000 90 45 *30 *23 *†18 *†15 *†13 *†12 *†10 *†9
1,100 80 40 *27 *20 *†16 *†14 *†12 *†10 *†9 *†8
1,200 70 35 *24 *†18 *†14 *†12 *†10 *†9 *†8 *†7
1,300 60 *30 *20 *†15 *†12 *†10 *†9 *†8 *†7 *†6
1,400 50 *25 *†17 *†13 *†10 *†9 *†8 *†7 *†6 *†5
1,500 40 *20 *†14 *†10 *†8 *†7 *†6 *†5 *†5 *†4
1,600 30 *†15 *†10 *†8 *†6 *†5 *†5 *†4 *†4 *†3
1,700 * *†10 *†7 *†5 *†4 *†4 *†3 *†3 *†3 *†2
1,800 *†10 *†5 *†4 *†3 *†2 *†2 *†2 *†2 *†2 *†1
1,900 *†0 *†0 *†0 *†0 *†0 *†0 *†0 *†0 *†0 *†0
2,000 -- -- -- -- -- -- -- -- -- --
2,100 -- -- -- -- -- -- -- -- -- --
2,200 -- -- -- -- -- -- -- -- -- --

veh/h/ln = vehicles per hour per lane.
-- = not applicable.
* Operator should consider initiating shoulder-opening activities.
† The freeway will reach capacity before the shoulder is opened.

Table 16. Minutes until Capacity is reached when per lane capacity is 1,800 veh/h/ln.
Bottleneck Per Lane Capacity Minutes until Capacity Is Reached
Increase in Hourly Volume Rate In Past 5 Minutes
1,800 10 20 30 40 50 60 70 80 90 100
Current Volume (veh/h/ln)
0 180 90 60 45 36 30 *26 *23 *20 *†18
100 170 85 57 43 34 *29 *25 *22 *†19 *†17
200 160 80 54 40 32 *27 *23 *20 *†18 *†16
300 150 75 50 38 *30 *25 *22 *†19 *†17 *†15
400 140 70 47 35 *28 *24 *20 *†18 *†16 *†14
500 130 65 44 33 *26 *22 *†19 *†17 *†15 *†13
600 120 60 40 *30 *24 *20 *†18 *†15 *†14 *†12
700 110 55 37 *28 *22 *†19 *†16 *†14 *†13 *†11
800 100 50 34 *25 *20 *†17 *†15 *†13 *†12 *†10
900 90 45 *30 *23 *†18 *†15 *†13 *†12 *†10 *†9
1,000 80 40 *27 *20 *†16 *†14 *†12 *†10 *†9 *†8
1,100 70 35 *24 *†18 *†14 *†12 *†10 *†9 *†8 *†7
1,200 60 *30 *20 *†15 *†12 *†10 *†9 *†8 *†7 *†6
1,300 50 *25 *†17 *†13 *†10 *†9 *†8 *†7 *†6 *†5
1,400 40 *20 *†14 *†10 *†8 *†7 *†6 *†5 *†5 *†4
1,500 30 *†15 *†10 *†8 *†6 *†5 *†5 *†4 *†4 *†3
1,600 * *†10 *†7 *†5 *†4 *†4 *†3 *†3 *†3 *†2
1,700 *†10 *†5 *†4 *†3 *†2 *†2 *†2 *†2 *†2 *†1
1,800 *†0 *†0 *†0 *†0 *†0 *†0 *†0 *†0 *†0 *†0
1,900 -- -- -- -- -- -- -- -- -- --
2,000 -- -- -- -- -- -- -- -- -- --
2,100 -- -- -- -- -- -- -- -- -- --
2,200 -- -- -- -- -- -- -- -- -- --

veh/h/ln = vehicles per hour per lane.
-- = not applicable.
* Operator should consider initiating shoulder-opening activities.
† The freeway will reach capacity before the shoulder is opened.

Table 17. Minutes until Capacity is reached when per lane capacity is 1,700 veh/h/ln.
Bottleneck Per Lane Capacity Minutes until Capacity Is Reached
Increase in Hourly Volume Rate In Past 5 Minutes
1,700 10 20 30 40 50 60 70 80 90 100
Current Volume (veh/h/ln)
0 170 85 57 43 34 *29 *25 *22 *†19 *†17
100 160 80 54 40 32 *27 *23 *20 *†18 *†16
200 150 75 50 38 *30 *25 *22 *†19 *†17 *†15
300 140 70 47 35 *28 *24 *20 *†18 *†16 *†14
400 130 65 44 33 *26 *22 *†19 *†17 *†15 *†13
500 120 60 40 *30 *24 *20 *†18 *†15 *†14 *†12
600 110 55 37 *28 *22 *†19 *†16 *†14 *†13 *†11
700 100 50 34 *25 *20 *†17 *†15 *†13 *†12 *†10
800 90 45 *30 *23 *†18 *†15 *†13 *†12 *†10 *†9
900 80 40 *27 *20 *†16 *†14 *†12 *†10 *†9 *†8
1,000 70 35 *24 *†18 *†14 *†12 *†10 *†9 *†8 *†7
1,100 60 *30 *20 *†15 *†12 *†10 *†9 *†8 *†7 *†6
1,200 50 *25 *†17 *†13 *†10 *†9 *†8 *†7 *†6 *†5
1,300 40 *20 *†14 *†10 *†8 *†7 *†6 *†5 *†5 *†4
1,400 30 *†15 *†10 *†8 *†6 *†5 *†5 *†4 *†4 *†3
1,500 * *†10 *†7 *†5 *†4 *†4 *†3 *†3 *†3 *†2
1,600 *†10 *†5 *†4 *†3 *†2 *†2 *†2 *†2 *†2 *†1
1,700 *†0 *†0 *†0 *†0 *†0 *†0 *†0 *†0 *†0 *†0
1,800 -- -- -- -- -- -- -- -- -- --
1,900 -- -- -- -- -- -- -- -- -- --
2,000 -- -- -- -- -- -- -- -- -- --
2,100 -- -- -- -- -- -- -- -- -- --
2,200 -- -- -- -- -- -- -- -- -- --

veh/h/ln = vehicles per hour per lane.
-- = not applicable.
* Operator should consider initiating shoulder-opening activities.
† The freeway will reach capacity before the shoulder is opened.

Table 18. Minutes until Capacity is reached when per lane capacity is 1,600 veh/h/ln.
Bottleneck Per Lane Capacity Minutes until Capacity Is Reached
Increase in Hourly Volume Rate In Past 5 Minutes
1,600 10 20 30 40 50 60 70 80 90 100
Current Volume (veh/h/ln)
0 160 80 54 40 32 *27 *23 *20 *†18 *†16
100 150 75 50 38 *30 *25 *22 *†19 *†17 *†15
200 140 70 47 35 *28 *24 *20 *†18 *†16 *†14
300 130 65 44 33 *26 *22 *†19 *†17 *†15 *†13
400 120 60 40 *30 *24 *20 *†18 *†15 *†14 *†12
500 110 55 37 *28 *22 *†19 *†16 *†14 *†13 *†11
600 100 50 34 *25 *20 *†17 *†15 *†13 *†12 *†10
700 90 45 *30 *23 *†18 *†15 *†13 *†12 *†10 *†9
800 80 40 *27 *20 *†16 *†14 *†12 *†10 *†9 *†8
900 70 35 *24 *†18 *†14 *†12 *†10 *†9 *†8 *†7
1,000 60 *30 *20 *†15 *†12 *†10 *†9 *†8 *†7 *†6
1,100 50 *25 *†17 *†13 *†10 *†9 *†8 *†7 *†6 *†5
1,200 40 *20 *†14 *†10 *†8 *†7 *†6 *†5 *†5 *†4
1,300 30 *†15 *†10 *†8 *†6 *†5 *†5 *†4 *†4 *†3
1,400 * *†10 *†7 *†5 *†4 *†4 *†3 *†3 *†3 *†2
1,500 *†10 *†5 *†4 *†3 *†2 *†2 *†2 *†2 *†2 *†1
1,600 *†0 *†0 *†0 *†0 *†0 *†0 *†0 *†0 *†0 *†0
1,700 -- -- -- -- -- -- -- -- -- --
1,800 -- -- -- -- -- -- -- -- -- --
1,900 -- -- -- -- -- -- -- -- -- --
2,000 -- -- -- -- -- -- -- -- -- --
2,100 -- -- -- -- -- -- -- -- -- --
2,200 -- -- -- -- -- -- -- -- -- --

veh/h/ln = vehicles per hour per lane.
-- = not applicable.
* Operator should consider initiating shoulder-opening activities.
† The freeway will reach capacity before the shoulder is opened.

Table 19. Minutes until Capacity is reached when per lane capacity is 1,500 veh/h/ln.
Bottleneck Per Lane Capacity Minutes until Capacity Is Reached
Increase in Hourly Volume Rate In Past 5 Minutes
1,500 10 20 30 40 50 60 70 80 90 100
Current Volume (veh/h/ln)
0 150 75 50 38 *30 *25 *22 *†19 *†17 *†15
100 140 70 47 35 *28 *24 *20 *†18 *†16 *†14
200 130 65 44 33 *26 *22 *†19 *†17 *†15 *†13
300 120 60 40 *30 *24 *20 *†18 *†15 *†14 *†12
400 110 55 37 *28 *22 *†19 *†16 *†14 *†13 *†11
500 100 50 34 *25 *20 *†17 *†15 *†13 *†12 *†10
600 90 45 *30 *23 *†18 *†15 *†13 *†12 *†10 *†9
700 80 40 *27 *20 *†16 *†14 *†12 *†10 *†9 *†8
800 70 35 *24 *†18 *†14 *†12 *†10 *†9 *†8 *†7
900 60 *30 *20 *†15 *†12 *†10 *†9 *†8 *†7 *†6
1,000 50 *25 *†17 *†13 *†10 *†9 *†8 *†7 *†6 *†5
1,100 40 *20 *†14 *†10 *†8 *†6 *†5 *†5 *†5 *†4
1,200 30 *†15 *†10 *†8 *†6 *†5 *†5 *†4 *†4 *†3
1,300 * *†10 *†7 *†5 *†4 *†4 *†3 *†3 *†3 *†2
1,400 *†10 *†5 *†4 *†3 *†2 *†2 *†2 *†2 *†2 *†1
1,500 *†0 *†0 *†0 *†0 *†0 *†0 *†0 *†0 *†0 *†0
1,600 -- -- -- -- -- -- -- -- -- --
1,700 -- -- -- -- -- -- -- -- -- --
1,800 -- -- -- -- -- -- -- -- -- --
1,900 -- -- -- -- -- -- -- -- -- --
2,000 -- -- -- -- -- -- -- -- -- --
2,100 -- -- -- -- -- -- -- -- -- --
2,200 -- -- -- -- -- -- -- -- -- --

veh/h/ln = vehicles per hour per lane.
-- = not applicable.
* Operator should consider initiating shoulder-opening activities.
† The freeway will reach capacity before the shoulder is opened.

 United States Department of Transportation - Federal Highway Administration