Norman W. Garrick

Forms of Trip Generation Models

Three Forms of Trip Generation Models are featured in the text

1. Regression ModelsA regression model is used to estimate the trip rate based on characteristics of the zone

2. Trip-Rate AnalysisTrip rate is estimated on characteristics of the trip generators with in the zone. Production rates are determined using the characteristics of the residential land uses and attraction rates using the characteristics of the nonresidential land uses

3. Cross-classification ModelsThis is a variation of the trip-rate analysis from

above. The difference is that the trip generation models (for the residential land uses) are disaggregate models

Norman W. Garrick

Form of the Cross-Classification Model

Trip rate for households with 4 persons and 1 vehicle is equal to 5.05 trips per day

Area Time Vehicle per Household 1 2,3 4 5+Urban High Density 0 0.50 2.05 4.60 7.00

1 1.45 2.95 5.05 7.902+ 1.85 3.55 5.75 8.35

Persons per HouseholdTotal Home-Based-Non Home Based Trip Rate

This model has two independent variables - persons/hh and vehicles/hh

Norman W. Garrick

Estimated No. of HH for Cross-Classification Model

Estimated number of households with 4 persons and 1 vehicle is 300

Area Time Vehicle per Household 1 2,3 4 5+Urban High Density 0 500 500 200 50

1 700 800 300 1002+ 300 500 400 100

Estimated Number of Households in Target Year in ZonePersons per Household

Norman W. Garrick

Trip Ends from Cross-Classification Models

Area Time Vehicle per Household 1 2,3 4 5+Urban High Density 0 250 1025 920 350

1 1015 2360 1515 7902+ 555 1775 2300 835

Total Home-Based-Non Home Based Trip in ZonePersons per Household

Estimated number of trips from households with 4 persons and 1 vehicle is (5.05*300) = 1515

Norman W. Garrick

Trip Rate Analysis

Trip-Rate AnalysisTrip rate is estimated on characteristics of the trip generators with in the zone. Production rates are determined using the characteristics of the residential land uses and attraction rates using the characteristics of the nonresidential land uses

Example from Text, Page 355, Table 8.2.1

The characteristics of the trip generator is given in 1000 SQ. FT.And the trip generation rate for each generator is given as TRIPS PER 1000

SQ. FT.

For exampleResidential: Total Sq. Ft. = 2744 1000 sq. ft., Trip Gen. Rate = 2.4 trips/1000

sq.ftTOTAL NO. of TRIP from residential land use = 2744*2.4 = 6586 Trips

Norman W. Garrick

ITE Trip Generation Manual

Norman W. Garrick

ITE Trip Generation ManualLow Rise Apartment, Weekday

Norman W. Garrick

ITE Trip Generation ManualLow Rise Apartment, Weekday

19 data points!

Norman W. Garrick

ITE Trip Generation ManualLimitations

The data contained in Trip Generation are, by definition, from

single-use developments where virtually all access is by private automobile and all parking is accommodated on site.

For new developments with characteristics that reduce automobile use--located close to transit, containing a mix of uses, or charging for parking--the use of unadjusted average ITE trip-generation rates will in many cases drastically overestimate the amount of traffic generated.

A corner store with no parking across from a subway station in a dense, transit-oriented development is often forecast to have the same impact as a 7-Eleven on a suburban highway.

Ref: Playing the numbers game: when it comes to TODs, trip-generation figures can make all the difference

by Millard-Ball, Adam, Siegman, Patrick http://www.entrepreneur.com/tradejournals/article/158211933.html

Norman W. Garrick

ITE Trip Generation ManualDangers of Overbuilding

"The traffic engineering profession is just waking up to the fact that one can overbuild infrastructure so it no longer serves the community," continues Walters (a California-based principal at Fehr & Peers Associates). "When one tries to design facilities to cater to the maximum demand that may occur, one can end up with too much.

"It's true of parking," Walters says. "It's also true of streets," where oversizing can lead to more lanes, wider lanes, and longer signal phases than are strictly warranted. This not only adds to development costs but reduces the amount of space available for trees and other amenities, and creates physical barriers in the community.

Ref: Playing the numbers game: when it comes to TODs, trip-generation figures can make all the difference

by Millard-Ball, Adam, Siegman, Patrick http://www.entrepreneur.com/tradejournals/article/158211933.html

Norman W. Garrick

Storrs Center

Norman W. Garrick

Storrs Center Google Earth The Site

Norman W. Garrick

Storrs Center Google Earth The Site Constraints

Wetlands

Forest Reserve

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Storrs Center Google Earth The Site Built Area

Norman W. Garrick

Storrs Center

Norman W. Garrick

Storrs Center Model

Norman W. Garrick

Storrs Center Model Village Road

Norman W. Garrick

Storrs Center Google Earth

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Storrs Center 195 Problem

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Storrs Center Importance of the

Network

Norman W. Garrick

Using TG Manual without Correction

Proposed Trip Generation

Dwelling UnitsHouses 131 DU 9.60 1,258

Town Houses 42 DU 5.60 235Live Work DU 42 DU 3.60 151Apartments 140 DU 6.70 938

CommercialLive Work 21,000 SF 11.60 244

Mixed Use 1 181,800 SF 44.32 8,057Mixed Use 2 181,800 SF 42.90 7,799

LodgingHotel 350 Rooms 8.90 3,115Civic

Town Hall 42,000 SF 34.00 1,428Library 30,000 SF 44.00 1,320Pool 5,150 SF 16.00 82

Totals 24,628

Daily Trips

Land Use Size Trip Generation Classification Trip Gen Rates Trip Gen

Single-Family Detached Housing (210)Condominium/Townhouse (230)Condominium/Townhouse (230)

Apartment (220)

Single Tenant Office (715)Specialty Retail Center (814)

Shopping Center (820)

Library (590)Recreation Center (495)

Hotel (310)

Government Office (730)

Estimated number of trip ends = 24,600

ITE Trip Generation Manual

Proposed size of project

Norman W. Garrick

Using TG Manual with Correction for Mixed Use

Proposed Trip Generation

Dwelling UnitsHouses 131 DU 9.60 1,258

Town Houses 42 DU 5.60 235Live Work DU 42 DU 3.60 151Apartments 140 DU 6.70 938

CommercialLive Work 21,000 SF 11.60 244

Mixed Use 1 181,800 SF 44.32 8,057Mixed Use 2 181,800 SF 42.90 7,799

LodgingHotel 350 Rooms 8.90 3,115Civic

Town Hall 42,000 SF 34.00 1,428Library 30,000 SF 44.00 1,320Pool 5,150 SF 16.00 82

Mixed Use Internal Capture -4,926Pass-by Trips -3,786

Totals 15,916

20 % of Residential, Commercial, Lodging and Civic Trips25 % of External Commercial and Civic Trips

Library (590)

Daily Trips

Trip GenLand Use SizeTrip Gen

RatesTrip Generation Classification

Single-Family Detached Housing (210)

Condominium/Townhouse (230)

Hotel (310)

Single Tenant Office (715)Specialty Retail Center (814)

Apartment (220)

Condominium/Townhouse (230)

Government Office (730)

Shopping Center (820)

Recreation Center (495)

Estimated number of trip ends = 15,900It is very important to remember that this total includes walking, biking and transit trips

Not just car trips