2010 San Benito County Traffic Modelsanbenitocog.org/agendas_minutes/cog/2014/March/COG_Item...The HPMS based VMT trend for San Benito County for various years in shown in Table 3

2010 San Benito County Traffic Model

HIGHWAY VALIDATION REPORT

Prepared for:

Council of San Benito County Governments

Prepared by:

Parsons March 2013 Revised November 2013

2010 San Benito County Traffic Model HIGHWAY VALIDATION REPORT

Prepared for:

Council of San Benito County Governments

Prepared by:

PARSONS

March 2013 Revised November 2013


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1. INTRODUCTION The San Benito County Traffic Model was developed in 1986 for use with establishing the first traffic impact fee for the county (Resolution 86-113). It has been used since that time for numerous traffic impact fee study updates, the Council of San Benito County Governments regional transportation plans, traffic studies for numerous roadway improvement projects (including the State Route 25 Hollister Bypass) and countless traffic impact studies for land development projects, including the Santana Ranch and Fairview Corners Specific Plans (2010 and 2011, respectively). The model has recently been updated to project future traffic associated with development growth within San Benito County, up to the year 2035. As a basis for the 2035 traffic forecasts, the model was validated to “existing conditions,” which represents the traffic volumes, roadway network, and land use characteristics which exist for the model validation year (2010 and 2011). The model validation indicated that the model was able to accurately replicate base year conditions and respond in the appropriate direction and magnitude when changes were made to input variables such as the roadway network. This document summarizes the results of this 2010 model validation update.


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2. MODEL VALIDATION Overview Travel model validation should focus on the entire travel modeling sequence—trip generation, trip distribution, mode choice, and trip assignment. In a typical model development process, the individual model components (trip generation, trip distribution, mode choice (or mode split), and time-of-day of travel) are calibrated using travel survey data and evaluated for reasonableness. After all of the model components are calibrated, the model is run as a system, including trip assignment. Assigned volumes are then compared to observed traffic counts for reasonability. The comparison to traffic counts, in effect, forms a “super” validation point. If the assigned traffic volumes do not reasonably match observed traffic counts, adjustments (such as those listed below) are made to the various model components to improve the match. The approach used for making model adjustments for validation purposes was to minimize the number and magnitude of the adjustments. Assigned traffic volumes will never exactly match observed traffic counts for several reasons. First, models are abstractions or simplifications of regional travel that can never account for all of the nuances of daily travel throughout the region. Second, traffic counts are not perfect. Traffic counts can easily vary by 10 percent or more depending on the day of the count, the time of year the count is performed, or the method used to perform the count. In addition, counts used for model validations are typically collected over several years due to the costs of counting traffic. Thus, matching traffic volumes on count locations within 10 to 15 percent is typically considered a success. Third, demographic information is not precise.

Demographic Information

The demographic data for the households and population was obtained from the 2010 census. Figure 1 illustrates the distribution of housing units in northern San Benito County as of 2010. Housing unit counts at the block level were obtained from the 2010 census and accumulated to larger “traffic analysis zones” or TAZ, which are used by the traffic model. Traffic analysis zones provide the spatial unit (or geographic area) within which travel behavior and traffic generation are estimated. The countywide model contains 413 traffic analysis zones and five cordon stations (points of entry and exit along highways at the perimeter of the modeling area). Figure 2 illustrates the distribution of non-farm employment (jobs) in northern San Benito County as of 2010. Job location data was obtained from the 2002 and 2004 updates of the San Benito/ Hollister Traffic Forecast Model files, the AMBAG Regional Travel Demand Model base year 2005 TAZ files, and field verification conducted in 2012. The total number of non-farm jobs for 2010 was normalized to State of California Employment Development Department estimates for the county. Given these land use inputs (number of housing units, retail and non-retail employment), the traffic model was run and the resulting traffic “forecasts” were compared with traffic count data and Caltrans’ estimates of vehicle miles traveled (VMT) in the county.


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Figure 1. Northern San Benito County 2010 Distribution of Dwelling Units


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Figure 2. Northern San Benito County 2010 Distribution of Non-farm Employment


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Highway Network

The 2010 highway network was updated from the 2000 San Benito County Traffic Model. The free flow speeds and capacities are reported in Table 1 and the updated highway network by facility type is shown in Figure 3.

Table 1: Year 2010 Highway Network Speed and Capacity Table

FACILITY TYPE

URBAN RURAL EXTERAL SPECIAL

SPEEDS CAPACITY SPEEDS CAPACITY SPEEDS CAPACITY SPEEDS CAPACITY

Freeways 55 1,500 60 1,500 65 1,500 60 1,500

Expressways 45 950 55 950 55 1,100 55 950

Major arterials 35 800 45 800 50 800 45 800

Minor arterials 30 600 40 600 45 600 40 600

Collector 25 500 35 500 45 500 35 500

Ramps 25 1,000 30 1,000 30 1,000 30 1,000

Centroids 15 9,999 15 9,999 15 9,999 15 9,999


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Figure 3. 2010 Highway Network Showing Facility Types


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Trip Generation

Table 2 shows the weekday daily person trips and the proportions of trips by purpose made by San Benito County and external county residents. Table 2: Year 2010 Validation Trip Generation Summary

TRIP PURPOSE

2010 MODEL

TRIPS PERCENT

Internal

Home-Based Work 49,384 18%

Home-based Non Work 162,260 60%

Non Home Based 52,911 19%

External




Total




Total Trips 271,725

Traffic Assignment Validation Model validation refers to comparing the model outputs (traffic volumes) to observed conditions (traffic counts and vehicle miles of travel estimates). During validation, adjustments are made primarily to model inputs, such as the road network and base year land uses, rather than calibrated parameters such as trip generation rates or peak factors. Once validated, the model can be used to predict future travel patterns with a high degree of confidence. The 2010 highway base year model results were validated using traffic counts collected in May 2011 for the SR 152 Trade Corridor Study and traffic counts collected during 2009 to 2011 for the 2035 San Benito County General Plan Draft Program EIR. The 2010 model validation targets are based on several criteria which are as follows:

� Comparison of modeled traffic volumes to observed traffic counts across facility types by percent volume deviation, with the maximum desirable deviation being 10 percent.

� Comparison of modeled VMT to estimates obtained from the Caltrans Highway Performance Monitoring System (HPMS), with the maximum deviation being three percent.

� Total volume and percent root mean square error (RMSE) by facility type and volume group should be less than 40 percent for appropriate aggregate group of links.


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� The percentage of links falling within the FHWA validation curve. The FHWA suggested link-specific validation criteria is that 75 percent of freeway and principal arterials (expressways), and 65 percent of all links should fall below the validation curve shown in Figure 4.

� Use the Federal Highway Administration and Caltrans recommended error limits for total error by functional classification (type of road) as a region-wide validation:

— Freeways less than 7 percent error — Expressways less than 10 percent error — Arterials less than 15 percent error — Collectors less than 25 percent error — Frontage roads less than 25 percent error

Figure 4. Maximum Desirable Error for Links


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All the above targets are specified for comparisons to the daily traffic volumes. The AM and PM peak periods were also compared, and in most cases, are well within the desired criteria. Traffic Counts The existing count data for the year 2010 model validation was counts collected from 2009 to 2011 as noted above. In all there were about 140 daily count locations by direction. Caltrans HPMS Caltrans prepares estimates of VMT for all roads in each California county for the HPMS. The VMT estimates are based on an extensive traffic counting program on a large sample of roads throughout the state. Local jurisdictions provide Caltrans with updates on the number of lane-miles of road within each classification type. Caltrans statistically extrapolates the traffic counts to provide estimates of total traffic volume on all lane-miles of each functional classification, and VMT. The HPMS based VMT trend for San Benito County for various years in shown in Table 3. This table indicates that the HPMS estimate of VMT for San Benito County in 2010 was 1,839,140. A detailed table showing 2010 HPMS based VMT by jurisdiction for San Benito County is shown in Table 4.

Table 3: HPMS Summary for San Benito County HPMS by Jurisdiction

YEAR

DAILY VEHICLE MILES OF TRAVEL

TOTAL HOLLISTER

SAN JUAN

BAUTISTA COUNTY ROADS

NATIONAL PARK

SERVICE STATE

HIGHWAYS

STATE PARK

SERVICE

2005 1,445,080 105,780 5,640 259,070 560 1,046,450 27,580

2006 1,483,230 101,460 5,640 258,550 450 1,089,550 27,580

2007 1,394,030 101,460 5,640 258,550 450 1,000,350 27,580

2008 1,387,050 101,420 7,300 258,550 440 991,760 27,580

2009 1,375,770 142,410 7,300 259,330 670 938,480 27,580

2010 1,839,150 142,410 7,300 259,330 670 1,401,860 27,580

2011 1,346,160 168,710 6,700 276,800 670 865,700 27,580

Source: Caltrans

Table 4: 2010 San Benito County HPMS by Jurisdiction

COUNTY/ LOCATION JURISDICTION

MAINTAINED MILES DAILY VEHICLE MILES

OF TRAVEL RURAL URBAN TOTAL RURAL URBAN TOTAL

Cities Hollister 0.00 95.00 95.00 0 142,410 142,410 San Juan Bautista 10.23 0.00 10.23 7,300 0 7,300 Other County 364.92 18.75 383.66 227,870 31,470 259,330 National Park Service 8.68 0.00 8.68 670 0 670 State Highways 83.97 6.11 90.08 1,375,600 26,250 1,401,860 State Park Service 306.40 0.00 306.40 27,580 0 27,580 774.20 119.85 894.05 1,639,020 200,130 1,839,150

Source: Caltrans 2010 Highway Performance Monitoring System


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The daily vehicle miles of travel reported in Tables 3 and 4 appear to contain a computational error under the “State Highway” entry for 2010 based on trend line data reported in Table 3. Table 3, which reports HPMS data published by Caltrans for year 2005 through 2011, indicates that annual average daily VMT, as computed by Caltrans, is typically in the ±1.4 million range for San Benito County. Independent estimates of annual average daily VMT on state highways (prepared by Parsons) places the 2010 total miles of travel at 949,824. This estimate is based on Caltrans published annual average daily traffic (AADT) volumes and highway link lengths for 2010. This calculation is confirmed by 2009–2011 traffic counts and link segment lengths assembled for the 2035 San Benito County General Plan Draft Program Environmental Impact Report, as updated by Parsons for the Highway 25 Widening Draft EIS/EIR Re-evaluation Traffic Study. This calculation produced a VMT estimate of 951,300 for state highways in San Benito County. Based on the above, Table 5 shows the updated HPMS VMT estimates for 2010. A more detailed table showing 2010 HPMS based VMT by jurisdiction for San Benito County is shown in Table 6.

Table 5: Updated HPMS Summary Based on Count Data

YEAR

DAILY VEHICLE MILES OF TRAVEL

TOTAL HOLLISTER

SAN JUAN

BAUTISTA COUNTY ROADS

NATIONAL PARK

SERVICE STATE

HIGHWAYS

STATE PARK

SERVICE 2010 1,387,114 142,410 7,300 259,330 670 949,824 27,580

Source: Parsons

Table 6: 2010 San Benito County HPMS by Jurisdiction (Updated)

COUNTY/ LOCATION JURISDICTION

MAINTAINED MILES DAILY VEHICLE MILES

OF TRAVEL

RURAL URBAN TOTAL RURAL URBAN TOTAL Cities Hollister 0 95.00 95.00 0 142,410 142,410 San Juan Bautista 10.23 0 10.23 7,300 0 7,300 Other County 364.92 18.75 383.66 227,870 31,470 259,330 National Park Service 8.68 0 8.68 670 0 670 State Highways 83.97 6.11 90.08 889,674 60,150 949,824 State Park Service 306.40 0 306.40 27,580 0 27,580

774.20 119.85 894.05 1,153,094 234,030 1,387,114 Source: Parsons

Vehicle Miles of Travel Vehicle miles of travel are calculated as the number of vehicles on a road segment multiplied by the length of the segment, summed over all road segments in a certain geographic area. The Caltrans HPMS estimates annual average daily vehicle miles of travel for each county in California based on a sample of traffic counts on various road types. A comparison of model-estimated VMT with VMT from the HPMS can indicate if the model is generating the correct magnitude of travel, even if there are inaccuracies in the specific road segment traffic volumes. Average weekday (Tuesday through Thursday) vehicle miles of travel are calculated from the San Benito County traffic model by multiplying link volumes times link distances. These model-generated estimates of average weekday VMT can then be compared to the HPMS AADT VMT estimates reported in Table 5. The model validation goal is that the VMT calculated from the


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model should be within three percent of the HPMS estimate. The 2010 model base year estimated 1,582,974 miles of vehicle travel for all highway links in the network (excluding centroid connectors) within San Benito County. The 2010 model VMT estimate, 1,582,974, is higher than the updated Caltrans HPMS estimate of 1,387,114 for San Benito County. A comparison of the two estimates is provided in Table 7. The modeled daily VMT estimates are over the acceptable range of plus or minus three percent. One possible reason for this increase is the larger highway network that is reflected in the travel forecast model. In other words, the number of roadway miles is significantly higher that the Caltrans estimates of roadway miles in the county.

Table 7: 2010 Daily VMT/VHT by Facility Type

ROAD TYPE

MODEL HPMS PERCENT

DIFFERENCE MODEL

VHT

MODEL AVERAGE

SPEED VMT ROAD MILES VMT

ROAD MILES VMT

ROAD MILES

Freeways 442,493 21.49 10,331 58.83 Expressways 479,820 52.79 9,575 50.11 Major arterials 448,055 142.83 11,695 38.31 Minor arterials 70,347 69.26 2,033 34.60 Collectors 138,528 351.92 4,492 30.84 Diamond ramps 3,731 1.72 124 29.98 Centroids* 96,756 433.08 6,450 15.00

Total—all roads 1,582,974 640.02 1,387,114 578.97** +14.12% +10.54% 35,441 40.45 Source: Parsons, San Benito County Traffic Model **Centroids not included in totals **Park roads not included

The comparisons presented in Table 7 indicate that the model generated estimates of VMT are 14.12 percent higher than the revised estimate of VMT reported for HPMS purposes. Excluding mileage associated with state and national park service roads, the mileage included in the travel forecast model is 10.54 percent greater than the road segment mileage reflected in the HPMS estimates of VMT. Thus, the two estimates of VMT may be closer to one another than they appear. In addition to the above comparison, Parsons investigated potential adjustments to the model estimates of average weekday (ADT) VMT versus the HPMS estimates of annual average daily traffic (AADT). For this exercise, a comparison was made of seven-day average daily traffic volumes versus Tuesday through Thursday average traffic volumes, based on 24-hour, 7-day traffic counts collected for the SR 152 Trade Corridor Project throughout northern San Benito County. The results of this investigation are presented in Table 8, and indicate that no adjustment in model generated VMT is warranted. In other words, for San Benito County, AADT estimates of VMT are equivalent to ADT estimates of VMT. By way of comparison, the AMBAG Regional Travel Demand Model was calibrated for a base year of 2005. The Caltrans-reported HPMS VMT for that year was 1,445,080. Runs of the 2005 AMBAG Base Year Model by Hexagon Transportation Consultants for the 2035 San Benito County General Plan Draft PEIR produced estimates of 1,772,012 of VMT for San Benito County. This estimate of VMT is 22.62 percent higher than the Caltrans-reported HPMS estimate.


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Table 8: 2010 San Benito County AADT versus ADT Comparison

FACILITY TYPE HPMS VMT (AADT) TUESDAY–THURSDAY:

7-DAY RATIO EQUIVALENT

WEEKDAY VMT (ADT) State Roads U.S. 101 390,821 0.9347 365,301 SR 1561 80,083 1.0297 82,461 SR 1562 224,885 0.9421 211,864 SR 253 187,887 1.0777 202,486 SR 254 39,766 0.9636 38,319 SR 146 1,264 NA 1,264 SR 129 25,118 1.0068 25,289

Total 949,824 0.9760 926,984 County Roads

Total 259,330 1.04545 271,102 City Roads

Total 149,710 1.04545 156,507 Other

Total 28,250 NA 28,250 TOTAL 1,387,114 0.9969 1,382,843

1U.S. 101 to Alameda 2Alameda to County Line 3Hollister to County Line 4South of Hollister 5Volume weighted average of 4th Street, Union Avenue, San Felipe Road, and Fairview Road.

The daily, AM peak and PM peak period VMT by facility type are shown in Table 9.

Table 9: AM Peak and PM Peak VMT/VHT by Facility Type

ROAD TYPE

AM PEAK HOUR PM PEAK HOUR

VMT VHT AVERAGE

SPEED VMT VHT AVERAGE

SPEED Freeways 29,909 505 59.26 35,803 612 58.51 Expressways 33,006 777 42.50 35,939 792 45.37 Major arterials 27,646 701 39.42 31,833 822 38.71 Minor arterials 4,844 136 35.54 5,166 147 35.15 Collectors 7,497 239 31.34 9,457 303 31.17 Diamond ramps 278 9 29.97 307 10 29.96 Centroids* 4,723 315 15.00 6,277 418 15.00

Total—All Roads 103,180 2,367 39.67 118,505 2,686 39.81 Source: Parsons, San Benito County Traffic Model (*centroids not included)

Traffic Assignment Validation The traffic assignment validation is conducted for daily, AM peak and PM peak period traffic conditions and is based on several criteria, including total volume by road type, percent of links within acceptable limits and VMT.


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The traffic counts and the model volumes are compared by facility type (Tables 10 through 12) and by the volume range in which they are classified (Tables 13 through 15). The comparison is made in terms of total model volume compared to total traffic counts and the root mean square error (RMSE), which is also used as a validation criterion.

Table 10: Daily Highway Validation by Road Type

ROAD TYPE NUMBER OF LINKS

TRAFFIC COUNTS

MODEL VOLUME

DIFFERENCE PERCENT CRITERIA

PERCENT RMSE

Freeways 10 225,040 226,637 0.71% ±7% Expressways 14 112,522 115,835 2.94% ±10% Major Arterials 60 268,795 262,591 –2.31% ±15% Minor Arterials 34 56,678 49,150 –13.28% ±25% Collectors 12 13,360 14,914 11.63% ±25%

Total—All Roads 130 676,395 669,127 –1.07% ±5% 19.23%

Table 11: AM Peak Highway Validation by Road Type


TRAFFIC COUNTS

MODEL VOLUME


PERCENT RMSE

Freeways 10 14,573 15,756 8.12% ±7% Expressways 12 6,237 6,820 9.35% ±10% Major Arterials 12 3,650 3,566 –2.30% ±15% Minor Arterials 8 721 866 20.11% ±25% Collectors 0 ±25%

Total—All Roads 42 25,181 27,008 7.26% ±5% 31.15%

Table 12: PM Peak Highway Validation by Road Type


TRAFFIC COUNTS

MODEL VOLUME


PERCENT RMSE

Freeways 10 16,764 18,281 9.05% ±7% Expressways 12 7,193 7,183 –0.14% ±10% Major Arterials 12 3,957 3,964 0.18% ±15% Minor Arterials 8 890 717 –19.44% ±25% Collectors 0 ±25%

Total—All Roads 42 28,804 30,145 4.66% ±5% 21.76%

Table 13: Highway Validation by Volume Range—Daily

VOLUME RANGE LINKS COUNT VOLUME DIFFERENCE

PERCENT CRITERIA PERCENT

RMSE <4,999 93 237,570 219,946 –7.42% 60%

>5,000 to <9,999 23 166,462 176,360 5.95% 41% >10,000 to <14,999 6 67,259 66,972 –0.43% 33% >15,000 to <19,999 0 0 0 0.00% 29% >20,000 to <24,999 4 84,560 86,215 1.96% 27% >25,000 to <29,999 2 56,050 52,958 –-5.52% 25% >30,000 to <34,999 2 64,494 66,676 3.38% 24%

Total—All 130 676,395 669,127 –1.07% 19.23%


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Table 14: Highway Validation by Volume Range—AM Peak



RMSE <500 28 6,074 6,682 10.01% 60%

>500 to <999 2 1,409 967 –31.37% 41% >1,000 to <1,499 8 9,762 11,196 14.69% 33% >1500 to <1,999 2 3,172 3,133 –1.23% 29% >2,000 to <2,499 1 2,110 1,767 –6.26% 27% >2,500 to <2,999 1 2,654 3,263 22.95% 25%

Total—All 42 25,181 27,008 7.26% 31.15%

Table 15: Highway Validation by Volume Range—PM Peak



RMSE <500 26 6,390 6,489 1.55% 60%

>500 to <999 5 3,626 3,230 –10.92% 41% >1,000 to <1,499 5 6,413 7,021 9.48% 33% >1,500 to <1,999 2 3,319 3,840 15.70% 29% >2,000 to <2,499 3 6,255 6,273 0.29% 27% >2,500 to <2,999 1 2,801 3,292 17.53% 25%

Total—All 42 28,804 30,145 4.66% 21.76%

The RMSE is a statistical indicator that is intended to represent the average percent error between an estimated value (such as a model volume) and an observed value (such as a traffic count). The RMSE is calculated as:

where:

n = the total number of links Ci = the observed count for road i Vi = the model volume for road i i = represents a road link

The RMSE provides a measure of accuracy based on the statistical standard deviation. The RMSE places a greater emphasis on larger errors that may cancel each other out in the comparison of total model volumes and traffic counts. The overall RMSE target is 30 percent. The 2010 model validation results meets the RMSE target for total volumes for daily, AM peak and PM peak validation scenarios.


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Percent Error by Facility Type and Volume Range The Federal Highway Administration and Caltrans recommended error limits for total error by functional classification (type of road) are as follows:

� Freeways: less than 7 percent error � Principal arterials: less than 10 percent error � Arterials: less than 15 percent error � Collectors: less than 25 percent error � Frontage roads: less than 25 percent error

The daily 2010 traffic validation reported in Table 10 meets the criteria for all facilities. The overall percent difference is one percent, which is well below the criteria of five percent. The 2010 traffic validation for the AM peak period reported in Table 11 shows the all the facilities except the freeways meet the allowable criteria listed above. The freeways are one percent higher. The overall percent difference is 72 percent above the allowable criteria of five percent. The 2010 traffic validation for the PM peak period reported in Table 12 shows that the all roadway facilities except the freeways meet the allowable criteria listed above. The freeways are two percent higher the criteria. The overall percent difference is five percent and is within the allowable criteria of five percent. The FHWA and Caltrans travel forecasting guidelines include a graphic showing the maximum desirable deviation between daily model volumes and traffic counts for individual link volumes (Figure 4). The maximum desirable deviations in total volume from the FHWA graphic are recommended for the validation by volume range and are included as criteria in the tables. � The suggested link-specific validation criteria are that 75 percent of the highway facilities

meet the maximum desirable deviation. � The 2010 model validation results show that 86 percent of links for daily, 75 percent for AM

peak and 83 percent for the PM peak hour meet the criteria for the maximum allowable deviation of at least 75 percent of links within acceptable deviation allowance. The summary results are shown in Table 16.

� The 2010 model validation results indicate a 19 percent RMSE for daily and 22 percent RMSE for the PM peak hour, which are below the allowable 30 percent RMSE. The AM peak hour RMSE is 31 percent, which is just above the threshold by one percent.

� The 2010 model validation results show a 0.97 correlation coefficient for daily, a 0.94 correlation coefficient for the AM peak hour and a 0.97 correlation coefficient for the PM peak hour. They all meet the criteria for the maximum allowable correlation coefficient of at least 0.88.

� The 2010 model validation results reported in Table 13 for the daily meets all the FHWA criteria for all of the volume ranges. The 2010 AM peak and PM peak model validations, reported in Tables 14 and 15, respectively, meet the FHWA criteria for all of the volume ranges.


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Therefore, the 2010 San Benito Travel Demand Model adequately meets the highway validation criteria for percent error.

Table 16: Highway Validation Summary

ONE-WAY LINK VALIDATION CRITERIA FOR ACCEPTANCE DAILY

AM PEAK HOUR

PM PEAK HOUR

Percent of links within Caltrans deviation allowance At least 75% 86% 75% 83%

Correlation coefficient At least 0.88 0.97 0.94 0.97

Percent root mean squared error Below 30% 19% 31% 22%

Traffic Assignment Results Figures 5 through 10 illustrate various results from the traffic assignment validation effort.


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Figure 5. 2010 Daily Differences Model minus Count


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Figure 6. 2010 AM Peak Hour Differences Model minus Count


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Figure 7. 2010 PM Peak Hour Differences Model minus Count


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Figure 8. 2010 Daily Traffic Volumes — Bandwidth


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Figure 9. 2010 AM Peak Hour Traffic Volumes — Bandwidth


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Figure 10. 2010 PM Peak Hour Traffic Volumes — Bandwidth

Documents

2010 San Benito County Traffic Modelsanbenitocog.org/agendas_minutes/cog/2014/March/COG_Item...The HPMS based VMT trend for San Benito County for various years in shown in Table 3