SUMMARY
The traffic analysis carried out by the Disney Corporation1 and its contractors in conjunction with specific input and direction from Prince William Transportation Staff and other officials, is the most reliable and up to date traffic analysis for Prince William County and the surrounding areas that has been accomplished.
The model, based on the gravity methodology, is known to provide reliable results. It was validated and calibrated using accurate traffic counts, many of which were made specifically for this study. For Prince William County, the model included a high level of detail in order to provide additional accuracy for roadways within the county. Other models and analyses, specifically the one carried out for the WTC are substantially inferior in accuracy, have not been adequately validated, have numerous discrepancies and contain major inconsistencies.
The road network used for the 2010 forecasts included existing roads, roads under construction and roads planned to be open to traffic by the year 2010. No roadway comparable to the Western Transportation Corridor is included in this network. The included 234 Bypass terminates at I-66. There is no major roadway north of I-66.
The Disney´s America Transportation Analysis demonstrates that north-south traffic needs are well served by the existing, under construction and planned roadways. The 234 bypass operates at Level of Service A (AM peak hours) or B (PM peak hours) in 2010. The analysis reveals that the only substantial roadway segments for which the LOS is unsatisfactory are along US-29, particularly west of the I-66 intersection at Gainesville, and Rte 234 between Balls Ford Road and I-66. The WTC facility does not mitigate the problem on these segments. There are no data in this study that support the need for the WTC. This remains true even in the scenario in which the Disney´s America theme park is constructed and attracts the projected number of visitors, and all of the ancillary hotels and housing are built to the allowed limit.
The planned improvements on I-66 west of Rte 234 and the improvements on US 29 will alleviate the US 29 problems. Building the Rte 28 Bypass could have a similar effect on Rte 234. The fact that the 234 Bypass does not alleviate the Rte 234 traffic is good evidence that the WTC facility would be equally ineffective. The rapidly declining rate of growth in population for PWC when projected to 2010 and 2020 reveals that the difference between the Disney´s America Traffic Analysis for 2010 and what is expected in 2020 is insignificant, and suggests that these traffic forecasts are overestimates.
ANALYSIS
Introduction
As part of the input to the Prince William Planning Board, Disney´s America was required to provide a comprehensive analysis of the impact of Disney´s America on the road network in the surrounding areas. In order to carry out this charge it was necessary to update the existing System II model by expanding its zone coverage in Prince William County. The network structure was greatly enhanced in Prince William County. Quoting from the report, "Again, the reason for the refined TAZ [Traffic Analysis Zones] structure within PWC is because the purpose of the model is to assess traffic conditions in the County at a more refined level than the regional model can produce."
The following analysis focuses primarily on the "Baseline Scenario." That is, it includes only the planned land uses existing in the approved 1990 Comprehensive Plan (and it updates to 1993) which do not involve the additional assumptions and changes needed to support the Disney´s America Theme Park. However, even in the "Baseline +" scenario, the results are unchanged except for the need for Road "A", a connector from the theme park to I-66.
Input for the model made use of COG Round 5.0 data outside of PWC and Round 5.1 approved data for PWC. Land use data for PWC was further refined using guidance from the Department of Public Works Transportation Division. These data were used to generate data for 1993. These data were the basis for the Counties´ input for the COG Round 5.3.2
Model Calibration (Validation)
This model was subjected to an extensive validation exercise using 1993 traffic counts from VDOT, PWC and addition counts on many secondary roads (including gravel roads such as Featherbed Lane.) Because virtually every road and intersection within the county was included in the model, a substantial effort to collect traffic counts had to be carried out.
At both the regional level and the local level, the agreement between actual traffic counts and model traffic counts was quite good as shown in Table 2.1.3 For highways that have large counts, the agreement is impressive. In all cases the agreement is much better than the established standard. In general the agreement at the 130 count locations within PWC was within 10% with an average difference of -8% countywide. Regional screen lines are critical for reliable projections. Similarly, for cordon lines, which measure how well the model predicts traffic on roads leading into the study area, the comparison is very good and well within the established national standards.
| Regional Screen Lines | Count | Model | % Diff |
| Potomac River Bridges | 797,000 | 766,943 | -3.8 |
| Occoquan River Bridges | 208,500 | 198,945 | -6.0 |
| Loudoun/Fairfax Line | 82,000 | 83,330 | 1.6 |
| Stafford/Prince William Line | 99,000 | 92,478 | -6.6 |
| Study Area | Cordon Lines | Count | Model Vol | % Diff |
| West | ||||
| I-66 | Rt 245 to US 15 | 20,000 | 19,582 | -2.0 |
| Rt 55 | Rt 681 to US 15 | 2,600 | 1,834 | -29.4 |
| US 29 | County Line to US 15 | 31,000 | 31,112 | 0.3 |
| Rt 28 | County Line to Rt 652 | 13,000 | 16,151 | 24.2 |
| Totals | 66,600 | 68,679 | 3.1 | |
| East | ||||
| I-66 | US 15 to US 29 | 24,000 | 23,118 | -3.6 |
| Rt 55 | Rt 625 to Rt 676 | 4,200 | 3,572 | -14.8 |
| US 29 | I-66 to Rt 705 | 4,500 | 3,912 | -13.0 |
| Totals | 32,700 | 30,602 | -6.8 | |
| North | ||||
| US 15 | Rt 234 to Rt 701 | 8,600 | 8,855 | 2.9 |
| South | ||||
| Rt 234 | NCL Manassas to I-66 | 41,000 | 39,813 | -2.8 |
Note: Table 2-4 is from the report PRINCE WILLIAM COUNTY TRANSPORTATION MODEL 2-10, page 6 prepared for DISNEY´S AMERICA.
Transportation Network
For future year traffic projections, the model requires that the network contain all existing highways, as well as roads planned to be opened to traffic before the model year, in this case the year 2010. These planned roads and road improvements include I-66 from 234 to the Beltway (now virtually complete), I-66 between 234 and the 234 Bypass (presently being studied), US 15 between Rte 55 to beyond Va 234 and US 29 west of I-66 to Rte 15 (in the planning stages as part of ISTEA.) Other than Road "A" no additional roads were needed to support Disney´s America.
The network did not include the extension of the 234 Bypass north of US 29, and most assuredly did not include the Western Transportation Corridor.
Land Use Information
Land use information developed specifically for MWCOG´s Round 5.3 was provided by PWC staff and input directly into the model (that is, no adjustments were made to this input data.) County officials state that they have high confidence in the validity of this input data.
Traffic Analysis
Using the validated model described above, and the updated land use information, the model was used to forecast daily traffic on roadway links, intersection turning movements and on interchange ramps for both the "Baseline" scenario and the "Baseline +" scenario. These daily traffic volumes are the baseline for developing peak hour traffic flows.
Table 3-14 in the Disney´s America Transportation Analysis Report is quite illuminating. It provides data on most of the major roads in the study area, which comprises Northern Prince William County. Only a limited amount of information is presented for roads south of I-66 and US 29, but it is sufficient to illustrate that there is no need for North-South roads other than those already planned or under construction. The following table is a selection of the data in the full report.
Note that the 234 Bypass has only 24,500 vehicles per day despite the fact that it serves essentially the same north-south needs as the WTC. In the "Baseline+" scenario, traffic increases to only 29,700. In 2010 it provides Level of Service (LOS) A for AM peak hours and LOS B for PM peak hours. It contributes insignificantly to US 29 and adds no traffic to I-66 east of Route 234, although presumably it reduces Rte. 234 traffic south of I-66. On other roads in the area, especially Rte 234 North of US 29, and segments of US 15, traffic is essentially unchanged in the "Baseline+" scenario.
| ROADWAY | SEGMENT | Lanes ("Base"/Base+") | Base Daily Traffic | Base+ Daily Traffic |
| I-66 | East of Rte 234 | 8LD* | 112,477 | 128,916 |
| I-66 | Rte 234 to Rte 234 Bypass | 6LD/8LD* | 79,834 | 103,742 |
| I-66 | Rte 234 Bypass to US Rte 29 | 4LD/8LD | 93,690 | 130,466 |
| I-66 | US Rte 29 to US Rte 15 | 4LD/6LD** | 44,077 | 78,071 |
| I-66 | US Rte 15 to Road "A" | 4LD/6LD** | 36,347 | 68,826 |
| I-66 | West of Road "A" | 4LD | 36,347 | 39,633 |
| US Rte 29 | North of Rt.234 | 2L | 12,883 | 11,580 |
| US Rte 29 | End of 4-L to Rt. 234 | 2L | 11,257 | 9,476 |
| US Rte 29 | North of I66 (4-Lane) | 4LD | 14,158 | 12,972 |
| US Rte 29 | I-66 to Route 55 | 6LD | 56,731 | 58,786 |
| US Rte 29 | Route 55 to Thoroughfare | 6LD | 53,968 | 54,865 |
| US Rte 29 | Thoroughfare to US Rte 15 | 6LD | 47,402 | 48,674 |
| US Rte 29 | US Rte 15 to Route 215 | 6LD | 57,984 | 59,791 |
| US Rte 15 | North of Route 234 | 4LD | 15,277 | 16,020 |
| US Rte 15 | Route 234 to Ent #1 | 4LD | 16,352 | 18,917 |
| US Rte 15 | Ent #1 to Artemus Rd | 4LD | 16,352 | 21,719 |
| US Rte 15 | Artemus Rd to Heathcote Rd | 4LD | 17,510 | 23,980 |
| US Rte 15 | Heathcote Ext to I-66 | 4LD | 19,496 | 28,866 |
| US Rte 15 | l-66 to Route 55 | 4LD | 19,598 | 22,195 |
| US Rte 15 | Route 55 to Thoroughfare | 2L | 14,743 | 15,343 |
| US Rte 15 | Thoroughfare to US 29 | 2L | 14,666 | 15,386 |
| Route 55 | US Rte 29 to Catharpin Rd | 2L | 8,978 | 10,479 |
| Route 55 | Catharpin Rd to US Rte 15 | 2L | 3,237 | 4,069 |
| Route 55 | US Rte 15 to Retail Ent | 2L | 4,440 | 9,632 |
| Route 55 | Retail Exit to Thoroughfare | 2L | 3,435 | 3,580 |
| Route 55 | Thoroughfare Rd to County Line | 2L | 3,924 | 5,810 |
| Route 234 | South of Rte 621 | 6LD | 49,475 | 49,331 |
| Route 234 | Rt. 621 to I-66 | 6LD | 56,056 | 56,205 |
| Route 234 | l-66 to US Rte 29 | 2L | 12,095 | 11,228 |
| Route 234 | Rte 29 to Rte 659 | 2L | 10,642 | 11,388 |
| Route 234 | Rte 659 to Rte 15 | 2L | 4,749 | 5,045 |
| Rte 234 Bypass | I-66 to Balls Ford Rd | 4LD | 24,489 | 29,743 |
| Balls Ford Rd (Rte 621) | Rte 234 Bypass to Rte 660 | 4LD | 13,274 | 10,211 |
| Balls Ford Rd (Rte 621) | Rte 660 to Rte 234 | 4LD | 12,472 | 11,952 |
| Balls Ford Rd (Rte 621) | East of Rte 234 | 4LD | 10,738 | 10,751 |
| Waterfall Dr | US Rte 15 to Rte 630 | 2L | 1,930 | 2,097 |
| Waterfall Dr | Rte 630 to Rte 68l | 2L | 412 | 615 |
| Waterfall Dr | Rte68l to Rte 600 | 2L | 721 | 2,045 |
| Rte 681 (Antioch Rd) | Waterfall to Thoroughfare | 2L | 849 | 2,386 |
| Rte 682 (Tboroughfare) | Rte 68l to Rte 55 | 2L | 151 | 4,428 |
| Rte 682 (Tboroughfare) | Rte 55 to US Rte 15 | 2L | 1,094 | 2,555 |
| Rte 682 (Tboroughfare) | US Rte 15 to Catharpin | 2L | 1,078 | 1,245 |
| Rte 682 (Tboroughfare) | Catharpin to US Rte 29 | 2L | 2,030 | 2,542 |
| Heathcote Drive Ext | Thoroughfare Rd to Road "A" | NA/4LD2 | NA | 4,352 |
| Heathcote Drive Ext | Road "A" to US Rte 15 | NA/4LD2 | NA | 20,659 |
| Heathcote Drive Ext | US Rte 15 to Catharpin Rd | 4LD | 3,493 | 7,127 |
| Heathcote Drive Ext | Catharpin Rd to US Rte 29 | 4LD | 7,365 | 6,645 |
| Catharpin Rd | Rte 234 toArtemus Rd | 2L | 1,241 | 1,436 |
| Catharpin Rd | Artemus Rd to Heathcote Dr | 2L | 6,522 | 6,486 |
| Catharpin Rd | Heathcote Dr to Rte 55 | 2L | 5,011 | 6,238 |
| Rte 705 (Pageland Ln) | Rte 234 to US Rte 29 | 2L | 212 | 542 |
| Rte 622 (Groveton Rd/Featherbed Ln) | Rte 234 to US Rte 29 | 2L | 2,353 | 3,761 |
| Rte 622 (Groveton Rd/Featherbed Ln) | US Rte 29 to Balls Ford Rd | 2L | 2,030 | 2,128 |
| Wellington Rd | Balls Ford Rd to Linton Hall | 4LD | 8,724 | 5,885 |
| Wellington Rd | Linton Hall to US Rte 29 | 4LD | 13,785 | 16,209 |
| Artemus Rd | Catharpin Rd to US Rte l5 | 2L | 1,538 | 2,196 |
| Road "A" | I-66 to Heathcote Drive | NA/6LD*** | NA | 40,721 |
| Road "A" | Heathcote Drive to End | NA/6LD*** | NA | 34,413 |
* Includes 6 general use Lanes and 2 HOV Lane
** Includes 4 general use Lanes and 2 HOV Lanes
*** Roadway does not exist in the "Base" Scenario
Examining the Peak Hour demands and the Level of Service results, it is apparent that the majority of the roadways and links operate at acceptable LOS in 2010. (Table 3-5.5) US 29 remains the most congested road, and of course it remains so if the WTC is built. The construction of additional lanes on I-66 west of Rte 234 is expected to mitigate this situation, but no valid traffic forecasts have been carried out for this case (The I-66 MIS is expected to contain such a study if COG´s regional traffic model can be modified and improved sufficiently to allow it to be validated.) But the recent opening of additional lanes on I-66 east of Rte 234 has dramatically reduced traffic on US 29 through the Manassas Battlefield Park, and additional lanes west of Rte 234 are likely to have a similar effect.
Rte 234 south of I-66 to Balls Ford Road suffers from congestion which is relieved only minimally by either the 234 Bypass or the WTC.
The forecasts indicate that the 2 lane section of Rte 15 (Rte 55 to US 29) will operate at LOS E in 2010 (the forecast exceeded LOS D by 30 vehicles per hour,) but the WTC study yields essentially the same result - LOS D for AM and PM peak hours.
The Disney´s America Transportation Analysis did not consider several regional roads that have been proposed or planned but are not in the Constrained Long Range Plan. The most important are the Tri-County Connector and the Rte. 28 Bypass. These roads in combination have essentially the same potential value as the WTC for traffic north of I-66, and would actually reduce travel mileage rather than increasing it as does the WTC.
Other Considerations
The Disney´s America Transportation Analysis forecasts were for the year 2010, and the WTCÕs were for the year 2020. It needs to be shown that the difference in these projections either are not significant or that the extrapolations needed to go from 2010 results to approximate 2020 results would not result in severe distortions. The Disney´s America Transportation Analysis and the WTC Traffic and Transportation Analysis use the same demographic data - Round 5.3 from the Metropolitan Washington Council of Governments (MWCOG). According to this data the population in Prince William County would grow from 367,200 in 2010 to 428,600 in 2020 - a 17% increase. An increase of this magnitude can be used to make extrapolations that are well within the errors expected in the models. (These models are not considered to have accuracies much better than 25% on average, so such an extrapolation, even if it had a large error, say 50%, would not be a substantial contributor to the expected model errors.)
The Disney´s America model was calibrated and validated for 1993 traffic counts. In contrast, the WTC model is poorly validated, has various glaring discrepancies, and uses 1990 traffic volume estimates rather than actual traffic counts.
Continued...Disney´s America Traffic Analysis
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1. Transportation Analysis for Disney´s America, May 1994
2. Personal Communication with PWC officials.
3. Transportation Analysis for Disney´s America, May 1994, page 2-10
4. ibid, page 3-4 (Table 3-1).
5. ibid, pages 3-23, 3-24.