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NCTC /Grass Valley Travel Demand Model Update
Nevada County Transportation Commission
September 2020
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Study GoalsTJKM was hired to update the travel model to the latest base year and develop forecasts
Review the existing Model, identify areas for improvement
Update the model from 2012 to 2018 Base year
Calibrate and Validate the 2018 Model
Develop Future Year 2040 Data and Traffic Forecasts
Documentation
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Travel ModelsA travel model is a statistical tool that uses existing demographic, land use and travel behavior data to forecast future traffic .
Forecasting Travel Demand is not simple. It involves many variables and complex relationships
Using rules of thumb and rapid assessment techniques is fine for short term, medium budget projects
For large scale investments, it is necessary to develop forecasts that have a proven technical basis.
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Modeling ProcessINPUTS
● Population ● Economy ● Land Use
OUTPUTS
Trip Generation (how many trips?)
Trip Distribution (Where do they go?)
Mode Choice (By what mode?)
Assignment (By what route?)
Traffic Flows on Network Links: Volumes and Speeds
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Why do we need a travel demand model?
• A typical regional model is necessary to answer questions like: What happens in next 20 -30 years? How policies/investments affect our answers? How will economic, demographic or land-use changes
affect transportation system performance? Update Traffic Impact Fees Traffic studies for development projects
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Roadway Networks and Zones
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Land use Data – 2018 (Residential)
2178
7505
31712102 2818
793
18264
0
2000
4000
6000
8000
10000
12000
14000
16000
18000
20000
Total Housing UnitsNevada City
6%
Grass Valley20%
Alta Sierra9%
Lake of the Pines6%Lake Wildwood
8%Penn Valley
2%
Unincorporated County
49%
Total Housing Units
Nevada City Grass Valley Alta Sierra
Lake of the Pines Lake Wildwood Penn Valley
Unincorporated County
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Land use Data – 2018 (Employment)
0 1000 2000 3000 4000 5000 6000
Nevada City
Grass Valley
Alta Sierra
Lake of the Pines
Lake Wildwood
Penn Valley
Unincorporated County
Landuse by Category (Thousand SQFT)
Office Medical Office Light Industrial
Warehouse Church Public/Quasi-Public
Retail Restaurant Fast Food Restaurant
Office 16% Medical Office
4%
Light Industrial 22%
Warehouse 5%
Church 5%
Public/Quasi-Public 5%
Retail 40%
Restaurant 2%
Fast Food Restaurant 1%Landuse by Category
Office Medical Office Light Industrial
Warehouse Church Public/Quasi-Public
Retail Restaurant Fast Food Restaurant
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Trip Data
HBW17%
HBO43%
NHB32%
SCHOOL6%
SIERRA2%
Trips by Purpose
HBW HBO NHB SCHOOL SIERRA
-
10.00
20.00
30.00
40.00
50.00
60.00
HBW HBO NHB SCH SIE HBWIE HBOIE NHBIE HBWEI HBOEI NHBEI XX
Average Travel Time (Minutes)
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Daily Highway Validation – Facility Type
Facility Type Observed Traffic Counts
2018 Estimated Volumes Daily Validation Targets
Sum of Counts Sum of Model Volumes % RMSE % Error % RMSE % Error
Freeways 323,834 348,700 17% 8% ~40% +/-15%
Principal Arterials 240,892 256,969 13% 7% +/-20%
Minor Arterials 546,199 551,949 36% 1% +/-25%
Major Collectors 342,817 348,034 45% 2% +/-25%
Minor Collectors 163,425 145,808 93% -11% +/-30%
Local 113,964 90,092 57% -21% +/-40%
All 1,731,132 1,741,552 42% 1% ~40% +/-15%
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Daily Highway Validation – JurisdictionFacility Type Observed Traffic Counts 2018 Estimated Volumes Daily Validation
Sum of Counts Sum of Model Volumes % Error
Grass Valley 794,476 792,538 0%
Nevada City 144,778 139,561 -2%
Alta Sierra 43,638 41,549 -5%
Lake Wildwood 2,804 2,261 -19%
Penn Valley 32,436 27,992 -14%
Unincorporated County 481,954 513,423 7%
Grass Valley SOI 107,581 103,381 -2%
Total 1,607,666 1,620,705 -7%
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2040 FORECASTS• Developed based on California Department of Finance, Caltrans Economic
Forecasts, inputs from NCTC staff and staff from cities• Annual growth of 0.32% per annum for Population and 0.54% per annum
for employment
36,831
7,708
13,165
39,515
8,787
14,381
0
5,000
10,000
15,000
20,000
25,000
30,000
35,000
40,000
45,000
Dwelling units Employment sqft (000) School / College Enrollment
Growth - 2018-2040
Base Year 2018 Forecast Year 2040
0
20,000
40,000
60,000
80,000
100,000
120,000
140,000
HBW HBO NHB SCHOOL SIERRACOLLEGE
Trips by Model Year and Purpose
Base Year 2018 Forecast Year 2040
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Growth in Volumes– Facility Type
Facility Type 2040 Estimated Volumes
2018 Estimated Volumes Difference Growth Rate
Freeways 366,208 348,700 17,508 0.22%
Principal Arterials 263,629 256,969 6,660 0.12%
Minor Arterials 605,342 551,949 53,393 0.42%
Major Collectors 379,750 348,034 31,716 0.40%
Minor Collectors 154,663 145,808 8,855 0.27%
Local 96,560 90,092 6,468 0.32%
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PM Period Volumes and congestion 2018
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PM Period Volumes and congestion 2040
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QUESTIONS?