part 2 processes and approaches associated with the fhwa method 1 1 hpms vehicle summary data
TRANSCRIPT
Part 2Processes and approaches associated
with the FHWA method
1
1
HPMS Vehicle Summary Data
How to Compute VMT
Traffic flow rate x roadway segment length = VMT
2
Flow rate examples100 vehicles per hour
Segment length examples10.15 miles
2
VMT Computation Example
1: Total annual average daily VMT =Annual average daily traffic (AADT) x roadway segment length
3
2: Total annual average daily combination truck VMT =Annual average daily CT traffic (AADT_CT) x roadway segment length
3
Example: VMT of Route 100
4
4
5
Example: VMT of Route 100
Segment ID
Beginning Mile Post
Ending Mile Post
Length (miles)
AADTCombination Truck AADT
1 0 20 20 1000 202 20 24 4 800 243 24 36 12 1200 684 26 38 12 1100 405 28 42 14 1400 1006 42 57 15 1000 287 57 82 25 1200 808 82 91 9 1600 609 91 99 8 1200 40
10 99 109 10 800 60Subtotal 129
5
6
Example: VMT of Route 100
Segment ID
Beginning Mile Post
Ending Mile Post
Length (miles)
AADTCombination Truck AADT
Total VMT
1 0 20 20 1,000 20 20,000 2 20 24 4 800 24 3,200 3 24 36 12 1,200 68 14,400 4 26 38 12 1,100 40 13,200 5 28 42 14 1,400 100 19,600 6 42 57 15 1,000 28 15,000 7 57 82 25 1,200 80 30,000 8 82 91 9 1,600 60 14,400 9 91 99 8 1,200 40 9,600
10 99 109 10 800 60 8,000 Subtotal 129 147,400
6
7
Example: VMT of Route 100
Segment ID
Beginning Mile Post
Ending Mile Post
Length (miles)
AADTCombination Truck AADT
Total VMT
CT VMT
1 0 20 20 1,000 20 20,000 400 2 20 24 4 800 24 3,200 96 3 24 36 12 1,200 68 14,400 816 4 26 38 12 1,100 40 13,200 480 5 28 42 14 1,400 100 19,600 1,400 6 42 57 15 1,000 28 15,000 420 7 57 82 25 1,200 80 30,000 2,000 8 82 91 9 1,600 60 14,400 540 9 91 99 8 1,200 40 9,600 320
10 99 109 10 800 60 8,000 600 Subtotal 129 147,400 7,072
7
8
Example: VMT of Route 100
Segment ID
Beginning Mile Post
Ending Mile Post
Length (miles)
AADTCombination Truck AADT
Total VMT
CT VMT
1 0 20 20 1,000 20 20,000 400 2 20 24 4 800 24 3,200 96 3 24 36 12 1,200 68 14,400 816 4 26 38 12 1,100 40 13,200 480 5 28 42 14 1,400 100 19,600 1,400 6 42 57 15 1,000 28 15,000 420 7 57 82 25 1,200 80 30,000 2,000 8 82 91 9 1,600 60 14,400 540 9 91 99 8 1,200 40 9,600 320
10 99 109 10 800 60 8,000 600 Subtotal 129 147,400 7,072
8
VMT computation is straightforward if AADT data for MC, Car, Light
Truck, Bus, SUT, and CT are known for
every segment of a roadway
9
9
10
Unfortunately we do not have such complete data!
The best we have is the HPMS link level
data. HPMS link level data contains:
1)AADT for all roadway segments,
2)AADT Single Unit Vehicle for sample and
NHS segments, and
3)AADT Combination Truck for sample and
NHS segments.
10
11
Example: VMT of Route 10011
What Available Are
12
Traffic classification count data outside HPMS outside HPMS for a given location – counts and % of various vehicles passing through a
counting point
Route 100=286 miles
Route 19
A
B
12
Route 100=286 miles
The Challenge
13
How to use such classification data to represent a system, an area, a state for VMT split?
Route 19
A
B
13
Method A – Simple Average
14
Simply add A and B together and divided it by 2 and use this simple average to represents the 286 miles long Route 100
Route 100=286 miles
Route 19
A
B
14
15
Route 100=286 miles
Method B – Weighted Average
15
Your local knowledge tells that Station A represents well for segment east of Route 19 which is 218 miles (total VMT of 1,015,226 miles).
Station B represents Route 100 well for the segment west of Route 19 (68 miles) with a total VMT of 641,376 miles.
Now you can use a weighted method. – weighting by VMT on each of the segment)
Route 19
A
B
15
Route 100=286 miles
Method B – Weighted Average
16
Route 19
A
B
16
Method B – Weighted Average
17
Route 100=286 miles
17
A
B
17
Route 100=286 miles
Route 19
A
B
Method B – Difference Between Weighted Average (WA) and Simple Average (SA)
18
A
18
The Importance of a Weighted Average
Weighted Average represents population more precise than Simple Average.
1: The more segments, the more precise of the weighting
2: The smaller the geography, the more precise of the weighting
FHWA defers to States on specific weighting segments, weighting VMT and geography.
19
19
Simple Average Weighted Average FHWA recommends Weighted Average
Summary
20
20