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90 Figure 23. Relationship between average internal travel distances and site size (Mockingbird Station, Atlantic Station, and Legacy Town Center). Use of Figure 22 requires information from a site plan show- 2nd edition (1). The recommended method enriches the ITE ing different land uses. During early stages of development method in the following manner: planning, it is unlikely that such a layout will always be avail- able; however, a development site will have been defined. Adds an A.M. peak-hour period to the existing P.M. peak- Hence, there is a need to be able to estimate travel distances hour period; for internal trips based on knowing only site size. Adds three land uses--restaurant, hotel, and cinema--to There is no end to the variety of potential site layouts for the existing office, retail, and residential uses; a given parcel of land, but reasonable assumptions can be Expands the basis for the A.M. and P.M. peak-hour internal made. In the case of internal trip capture estimation, it is capture factors from three developments in one state to six prudent to err on the conservative side--that is, to under- developments in three states and also broadens the types of estimate internal capture rather than to overestimate capture. MXDs included in the database; and A few basic assumptions to arrive at a maximum travel dis- Adds a proximity adjustment for some land use pairs. tance can be applied. These could include a distance from the property boundary to the building doors and the internal Midday and daily periods, which are included in the ITE block configuration. Trip Generation Handbook, were not addressed since those Figure 23 shows the site size and average separation dis- periods are rarely used in typical TIS and would have increased tances between interacting land uses for Mockingbird Sta- the data collection cost beyond the available resources. The tion, Atlantic Station, and Legacy Town Center. The straight recommended estimation method consists of the following line relationship may be coincidental since there are differ- basic steps: ences in the site configurations and layouts of the component 1. Determine whether the methodology is appropriate for land uses. Figure 23 may provide a basis for estimating sepa- the development to be analyzed. ration distances if there is no site plan or conceptual land use 2. Define the pertinent site and development characteristics. plan available when an analysis is performed, but this should 3. Estimate single-use trip generation for each component be validated and refined in further studies. land use using ITE or other acceptable source; convert to person trips. Procedure for Estimating Internal 4. Use unconstrained internal capture percentages devel- Capture at a Proposed MXD oped in this project to estimate the number of potential internal trips between each pair of land uses. Include an The estimation procedure developed in this project is adjustment for proximity (also developed in this project). essentially an extension and enhancement of the current ITE 5. Balance internal trips generated at both ends of each inter- method documented in the ITE Trip Generation Handbook, acting pair (i.e., internal trips coming from the origin end

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91 need to be the same as those coming to the destination Step 5: Calculate the balanced internal trips between all end); adapt the existing balancing procedure contained in land use pairs. the ITE Trip Generation Handbook (1). Step 6: Calculate the overall internal capture rate for 6. Subtract the estimated internal trips from the total trip the site. generation to estimate external trips for the MXD being analyzed; convert to vehicle trips as needed. One product of this procedure is an estimate of internal trip capture between pairs of land uses in the development for The user of this estimation methodology is cautioned that which internal capture data exist. Users of this estimation each MXD has unique characteristics that influence the extent procedure are encouraged to carefully and completely read of internal trip capture. Such characteristics include, but are earlier parts of this chapter to understand the background not limited to the following: and data supporting this procedure: The number and magnitudes of complementary land uses; The internal capture estimation methodology and its logic, The layout of the land uses relative to each other; Descriptions of the six developments from which the data Specific businesses, residence types, and other component behind the estimation methodology were collected, characteristics within each land use category; Survey findings from the six development sites, and Proximity and connectivity between each pair of land uses; The following instructions for use of the estimation Design characteristics of the development and its internal methodology. transportation system; Specific characteristics of the development's access and If the analyst understands the concept of "internal cap- parking; and ture balancing" as described earlier in this chapter, these basic Competing opportunities outside the development. instructions should suffice. At the end of this chapter, addi- tional guidance is provided for the analyst who understands The user is further cautioned that estimates of internal cap- the concepts, but who is unsure of the mechanics of a specific ture for trips between specific pairs of land uses are based on step. Additional guidance is also provided for the analyst who data collected for between one and six surveyed develop- thoroughly understands the basic concept and its data limita- ments. Clearly, additional data on internal capture at existing tions, appreciates the uniqueness of each mixed-use site, and MXDs would help improve confidence in the accuracy of the is interested in investigating the potential internal capture internal capture estimates and might result in different inter- impacts of the nuances of a particular site. nal capture rates. Tables 103 through 106 show an automated spreadsheet The researchers believe that the successful but limited val- tool that can be used to compute internal capture and exter- idations conducted for this estimation method do confirm that the results provide accurate approximations of external nal trip generation for MXDs. The entire workbook consists trip generation for typical MXDs consisting of typical office, of six separate worksheets in two sets--one for weekday A.M. retail, restaurant, residential, cinema, and hotel land uses. street peak-hour estimates and one for weekday P.M. street The researchers also believe these approximations are con- peak-hour estimates. This description covers the A.M. street sistent with the accuracy of trip generation estimates for peak hour only. The six worksheet and tables in which the single-use developments as portrayed in such references as A.M. sheets are shown are Trip Generation, 8th edition (2). The researchers also believe this methodology provides an advancement and improve- Table 103 (Worksheet 1): Estimator Input/Output Work- ment over a similar method described in Trip Generation sheet--A.M. Street Peak Hour; Handbook, 2nd edition (1). Not shown here (Worksheet 2): Estimator Input/Output The estimation procedure is presented step-by-step in the Worksheet--P.M. Street Peak Hour; order it would be performed by the analyst: Table 104 (Worksheet 3): Estimator Intermediate Calcu- lations--A.M. Street Peak Hour; Step 1: Determine whether the methodology is appropri- Not shown here (Worksheet 4): Estimator Intermediate ate for your application. Calculations--P.M. Street Peak Hour; Step 2: Define the pertinent site characteristics. Table 105 (Worksheet 5): Estimator Updated ITE Trip Gen- Step 3: Calculate single-use trip generation for the site eration Handbook Table 7.1 With Proximity Adjustment components. (1, Ch. 7); and Step 4: Estimate the unconstrained internal capture rates Table 106 (Worksheet 6): Estimator Updated ITE Trip for all land use pairs at the site and add adjustments for Generation Handbook Table 7.2 With Proximity Adjust- proximity. ment (1, Ch. 7).

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92 Table 103. Estimator input/output worksheet--A.M. street peak hour (A.M. sheet 1 of 4). NCHRP 8-51 Internal Trip Capture Estimator Project Name: Organization: Project Location: Performed By: Scenario Description: Date: Analysis Year: Checked By: Analysis Period: AM Street Peak Hour Date: Table 1-A: Base Vehicle-Trip Generation Estimates (Single-Use Site Estimate) Development Data (For Information Only ) Estimated Vehicle-Trips Land Use ITE LUCs 1 Quantity Units Total Entering Exiting Office 0 Retail 0 Restaurant 0 Cinema/Entertainment 0 Residential 0 Hotel 0 All Other Land Uses 2 0 Total 0 0 0 Table 2-A: Mode Split and Vehicle Occupancy Estimates Entering Trips Exiting Trips Land Use Veh. Occ. % Transit % Non-Motorized Veh. Occ. % Transit % Non-Motorized Office Retail Restaurant Cinema/Entertainment Residential Hotel 2 All Other Land Uses Table 3-A: Average Land Use Interchange Distances (Feet Walking Distance) Destination (To) Origin (From) Office Retail Restaurant Cinema/Entertainment Residential Hotel Office Retail Restaurant Cinema/Entertainment Residential Hotel Table 4-A: Internal Person-Trip Origin-Destination Matrix Destination (To) Origin (From) Office Retail Restaurant Cinema/Entertainment Residential Hotel Office 0 0 0 0 0 Retail 0 0 0 0 0 Restaurant 0 0 0 0 0 Cinema/Entertainment 0 0 0 0 0 Residential 0 0 0 0 0 Hotel 0 0 0 0 0 Table 5-A: Computations Summary Table 6-A: Internal Trip Capture Percentages by Land Use Total Entering Exiting Land Use Entering Trips Exiting Trips All Person-Trips Office Internal Capture Percentage Retail Restaurant External Vehicle-Trips 3 Cinema/Entertainment External Transit-Trips 4 Residential External Non-Motorized Trips 4 Hotel 1 Land Use Codes (LUCs) from Trip Generation Informational Report , published by the Institute of Transportation Engineers. 2 Total estimate for all other land uses at mixed-use development site-not subject to internal trip capture computations in this estimator 3 Vehicle-trips computed using the mode split and vehicle occupancy values provided in Table 2-A 4 Person-Trips Estimator Tool Developed by the Texas Transportation Institute for NCHRP Project 8-51

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93 Table 104. Estimator intermediate calculations--A.M. street peak hour (A.M. sheet 2 of 4). Project Name: Analysis Period: AM Street Peak Hour Table 7-A: Conversion of Vehicle-Trip Ends to Person-Trip Ends Table 7-A (D): Entering Trips Table 7-A (O): Exiting Trips Land Use Veh. Occ. Vehicle-Trips Person-Trips Veh. Occ. Vehicle-Trips Person-Trips Office Retail Restaurant Cinema/Entertainment Residential Hotel Table 8-A (O): Internal Person-Trip Origin-Destination Matrix (Computed at Origin) Destination (To) Origin (From) Office Retail Restaurant Cinema/Entertainment Residential Hotel Office 0 0 0 0 0 Retail 0 0 0 0 0 Restaurant 0 0 0 0 0 Cinema/Entertainment 0 0 0 0 0 Residential 0 0 0 0 0 Hotel 0 0 0 0 0 Table 8-A (D): Internal Person-Trip Origin-Destination Matrix (Computed at Destination) Destination (To) Origin (From) Office Retail Restaurant Cinema/Entertainment Residential Hotel Office 0 0 0 0 0 Retail 0 0 0 0 0 Restaurant 0 0 0 0 0 Cinema/Entertainment 0 0 0 0 0 Residential 0 0 0 0 0 Hotel 0 0 0 0 0 Table 9-A (D): Internal and External Trips Summary (Entering Trips) Person-Trip Estimates External Trips by Mode Destination Land Use Internal External Total Vehicles1 Transit2 Non-Motorized2 Office Retail Restaurant Cinema/Entertainment Residential Hotel All Other Land Uses 3 Table 9-A (O): Internal and External Trips Summary (Exiting Trips) Person-Trip Estimates External Trips by Mode Origin Land Use Internal External Total Vehicles1 Transit2 Non-Motorized2 Office Retail Restaurant Cinema/Entertainment Residential Hotel All Other Land Uses 3 1 Vehicle-trips computed using the mode split and vehicle occupancy values provided in Table 2-A 2 Person-Trips 3 Total estimate for all other land uses at mixed-use development site-not subject to internal trip capture computations in this estimator

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Table 105. Estimator updated ITE Trip Generation Handbook (1, p. 93) Table 7.1 with proximity adjustment (sheet 3 of 4). Table 7.1 Unconstrained Internal Trip Capture Rates for Trip Origins within a Table 7.1a Adjusted Internal Trip Capture Rates for Trip Origins within a Multi- Proximity Multi-Use Development Use Development Adjustment Weekday Weekday Land Use Pairs Land Use Pairs AM Peak Hour PM Peak Hour AM PM AM Peak Hour PM Peak Hour To Office 0% 0% 1.000 1.000 To Office 0.0% 0.0% To Retail 28% 20% 1.000 1.000 To Retail 28.0% 20.0% To Restaurant 63% 4% 1.000 1.000 To Restaurant 63.0% 4.0% From OFFICE From OFFICE To Cinema/Entertainment 0% 0% 1.000 1.000 To Cinema/Entertainment 0.0% 0.0% To Residential 1% 2% 1.000 1.000 To Residential 1.0% 2.0% To Hotel 0% 0% 1.000 1.000 To Hotel 0.0% 0.0% To Office 29% 2% 1.000 1.000 To Office 29.0% 2.0% To Retail 0% 0% 1.000 1.000 To Retail 0.0% 0.0% To Restaurant 13% 29% 1.000 1.000 To Restaurant 13.0% 29.0% From RETAIL From RETAIL To Cinema/Entertainment 0% 4% 1.000 1.000 To Cinema/Entertainment 0.0% 4.0% To Residential 14% 26% 1.000 1.000 To Residential 14.0% 26.0% To Hotel 0% 5% 1.000 1.000 To Hotel 0.0% 5.0% To Office 31% 3% 1.000 1.000 To Office 31.0% 3.0% To Retail 14% 41% 1.000 1.000 To Retail 14.0% 41.0% To Restaurant 0% 0% 1.000 1.000 To Restaurant 0.0% 0.0% From RESTAURANT From RESTAURANT To Cinema/Entertainment 0% 8% 1.000 1.000 To Cinema/Entertainment 0.0% 8.0% To Residential 4% 18% 1.000 1.000 To Residential 4.0% 18.0% To Hotel 3% 7% 1.000 1.000 To Hotel 3.0% 7.0% To Office 0% 2% 1.000 1.000 To Office 0.0% 2.0% To Retail 0% 21% 1.000 1.000 To Retail 0.0% 21.0% From CINEMA/ To Restaurant 0% 31% 1.000 1.000 From CINEMA/ To Restaurant 0.0% 31.0% ENTERTAINMENT To Cinema/Entertainment 0% 0% 1.000 1.000 ENTERTAINMENT To Cinema/Entertainment 0.0% 0.0% To Residential 0% 8% 1.000 1.000 To Residential 0.0% 8.0% To Hotel 0% 2% 1.000 1.000 To Hotel 0.0% 2.0% To Office 2% 4% 1.000 1.000 To Office 2.0% 4.0% To Retail 1% 42% 1.000 1.000 To Retail 1.0% 42.0% To Restaurant 20% 21% 1.000 1.000 To Restaurant 20.0% 21.0% From RESIDENTIAL From RESIDENTIAL To Cinema/Entertainment 0% 0% 1.000 1.000 To Cinema/Entertainment 0.0% 0.0% To Residential 0% 0% 1.000 1.000 To Residential 0.0% 0.0% To Hotel 0% 3% 1.000 1.000 To Hotel 0.0% 3.0% To Office 75% 0% 1.000 1.000 To Office 75.0% 0.0% To Retail 14% 16% 1.000 1.000 To Retail 14.0% 16.0% To Restaurant 9% 68% 1.000 1.000 To Restaurant 9.0% 68.0% From HOTEL From HOTEL To Cinema/Entertainment 0% 0% 1.000 1.000 To Cinema/Entertainment 0.0% 0.0% To Residential 0% 2% 1.000 1.000 To Residential 0.0% 2.0% To Hotel 0% 0% 1.000 1.000 To Hotel 0.0% 0.0%

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Table 106. Estimator updated ITE Trip Generation Handbook Table 7.2 with proximity adjustment (sheet 4 of 4). Table 7.2 Unconstrained Internal Trip Capture Rates for Trip Destinations within Table 7.2a Adjusted Internal Trip Capture Rates for Trip Destinations within a Proximity a Multi-Use Development Multi-Use Development Adjustment Weekday Weekday Land Use Pairs Land Use Pairs AM Peak Hour PM Peak Hour AM PM AM Peak Hour PM Peak Hour From Office 0% 0% 1.000 1.000 From Office 0.0% 0.0% From Retail 4% 31% 1.000 1.000 From Retail 4.0% 31.0% From Restaurant 14% 30% 1.000 1.000 From Restaurant 14.0% 30.0% To OFFICE To OFFICE From Cinema/Entertainment 0% 6% 1.000 1.000 From Cinema/Entertainment 0.0% 6.0% From Residential 3% 57% 1.000 1.000 From Residential 3.0% 57.0% From Hotel 3% 0% 1.000 1.000 From Hotel 3.0% 0.0% From Office 32% 8% 1.000 1.000 From Office 32.0% 8.0% From Retail 0% 0% 1.000 1.000 From Retail 0.0% 0.0% From Restaurant 8% 50% 1.000 1.000 From Restaurant 8.0% 50.0% To RETAIL To RETAIL From Cinema/Entertainment 0% 4% 1.000 1.000 From Cinema/Entertainment 0.0% 4.0% From Residential 17% 10% 1.000 1.000 From Residential 17.0% 10.0% From Hotel 4% 2% 1.000 1.000 From Hotel 4.0% 2.0% From Office 23% 2% 1.000 1.000 From Office 23.0% 2.0% From Retail 50% 29% 1.000 1.000 From Retail 50.0% 29.0% From Restaurant 0% 0% 1.000 1.000 From Restaurant 0.0% 0.0% To RESTAURANT To RESTAURANT From Cinema/Entertainment 0% 3% 1.000 1.000 From Cinema/Entertainment 0.0% 3.0% From Residential 20% 14% 1.000 1.000 From Residential 20.0% 14.0% From Hotel 6% 5% 1.000 1.000 From Hotel 6.0% 5.0% From Office 0% 1% 1.000 1.000 From Office 0.0% 1.0% From Retail 0% 26% 1.000 1.000 From Retail 0.0% 26.0% To CINEMA/ From Restaurant 0% 32% 1.000 1.000 To CINEMA/ From Restaurant 0.0% 32.0% ENTERTAINMENT From Cinema/Entertainment 0% 0% 1.000 1.000 ENTERTAINMENT From Cinema/Entertainment 0.0% 0.0% From Residential 0% 0% 1.000 1.000 From Residential 0.0% 0.0% From Hotel 0% 0% 1.000 1.000 From Hotel 0.0% 0.0% From Office 0% 4% 1.000 1.000 From Office 0.0% 4.0% From Retail 2% 46% 1.000 1.000 From Retail 2.0% 46.0% From Restaurant 5% 16% 1.000 1.000 From Restaurant 5.0% 16.0% To RESIDENTIAL To RESIDENTIAL From Cinema/Entertainment 0% 4% 1.000 1.000 From Cinema/Entertainment 0.0% 4.0% From Residential 0% 0% 1.000 1.000 From Residential 0.0% 0.0% From Hotel 0% 0% 1.000 1.000 From Hotel 0.0% 0.0% From Office 0% 0% 1.000 1.000 From Office 0.0% 0.0% From Retail 0% 17% 1.000 1.000 From Retail 0.0% 17.0% From Restaurant 4% 71% 1.000 1.000 From Restaurant 4.0% 71.0% To HOTEL To HOTEL From Cinema/Entertainment 0% 1% 1.000 1.000 From Cinema/Entertainment 0.0% 1.0% From Residential 0% 12% 1.000 1.000 From Residential 0.0% 12.0% From Hotel 0% 0% 1.000 1.000 From Hotel 0.0% 0.0%