demand forecasting 2008

Transportation Engineering

Transportation Planning Process

Transportation Planning

What are some examples of goals and objectives for a

transportation system?

Transportation Planning

Forecasting Travel

How do we know what travel behavior will be like in 20

years?

Defining Study AreaDelineate boundaries and subdivide into zonesZones Should Have Following Characteristics

Homogeneous Socioeconomic Characteristics Intrazonal Trips Should Be MinimizedUse Physical, Political, and Historical Boundaries if

PossibleZones Should Not Be Created Within Other ZonesThe Zone System Should Generate and Attract

Approximately Equal Trips, Households, Population,or Area

Use Census Tract Boundaries Where Possible.

Example for TAZs

Forecasting TravelPopulation and Economic Data

Transportation Inventories

Travel Surveys

Forecasting TravelCalibration

Establishing a mathematical relationship to estimate future travel demand

Trip Estimation ExampleA multiple regression analysis shows the

following relationship for the number of trips per household:

T = 0.82 + 1.3P + 2.1AT = Trips per household per dayP = persons per householdA = Autos per household

Zone contains 250 households with an average of 4 persons and 2 autos for each household, determine the average number of trips per day in that zone .

Transportation PlanningEnvironmental Impact Statements

Purpose and NeedAlternativesEnvironmental Effects

Highway EngineeringForecasting Travel Demand

Growth Rate Methods (Rural)Urban and Intercity Travel Forecasting

Forecasting Travel DemandFactors Influencing Travel DemandLocation and intensity of land useSocioeconomic Characteristics of the population

Extent, Cost, and Quality of the available transportation

Forecasting Travel Demand

What are some factors that affect how much you

travel?

Forecasting Travel Demand

Forecasting Travel DemandTrip generation

Process for determining the number of trips that will begin and end in each traffic zone.

Trip GenerationTrip EndTrip ProductionTrip Attraction

Trip GenerationClassification of Trips

Home-Based Work (HBW)Home-Based Other (HBO)Non Home Based (NHB)

Trip GenerationTwo functions of trip generation

Develop a relationship between trip end production or attraction and land use

Use the relationship developed to estimate the number of trips generated at some future date under a new set of land-use conditions

Trip GenerationCross classification method of trip generationDevelop relationship between socioeconomic measures and trip generation

Trip Generation ExampleDevelop a set of curves showing the

number of trips per household versus income and auto ownership.

Trip Generation ExampleHousehold #Household # Trips ProducedTrips Produced Income ($1000)Income ($1000) AutosAutos

11 22 1616 0022 44 2424 0033 1010 6868 2244 55 4444 0055 55 1818 1166 1515 6868 3377 77 3838 1188 44 3636 0099 66 2828 11

1010 1313 7676 331111 88 7272 111212 66 3232 111313 99 2828 221414 1111 4444 221515 1010 4444 221616 1111 5252 221717 1212 6060 221818 88 4444 111919 88 5252 112020 66 2828 11

Trip Generation Example

Income Income ($1000)($1000)

Autos OwnedAutos OwnedTotal Total

00 11 2+2+

2424 2 (67)2 (67) 1 1 (33)(33) 0 (0)0 (0) 3 (100)3 (100)

24 – 3624 – 36 1 (20)1 (20) 3 3 (60)(60)

1 1 (20)(20) 5 (100)5 (100)

36 – 4836 – 48 1 (20)1 (20) 2 2 (40)(40)

2 2 (40)(40) 5 (100)5 (100)

48 – 6048 – 60 0 (0)0 (0) 1 1 (33)(33)

2 2 (67)(67) 3 (100)3 (100)

> 60> 60 0 (0)0 (0) 1 1 (25)(25)

3 3 (75)(75) 4 (100)4 (100)

TotalTotal 44 88 88 2020

Number & Percent of Household in Each Income Category Versus Car Ownership


Income Income ($1000($1000

))

Autos OwnedAutos Owned

00 11 2 +2 +

<24<24 33 55 ----24 – 3624 – 36 44 66 9936 – 4836 – 48 55 7.57.5 10.510.548 – 6048 – 60 ---- 8.58.5 11.511.5

>60>60 -- -- 8.58.5 12.712.7

Average Trips per Household Versus Income and Car

Ownership


Trips per Household per Day by Auto Ownership and Income

Category


Trips by Purpose and Income Category

Trip Generation ExampleDetermine the number of trips per day

generated for each trip purpose. Number of dwelling units: 60Average income per dwelling unit: $44,000

Income ($)Income ($) HouseholHouseholdsds

Low (under 32,000)Low (under 32,000) 99

Medium (32,000 – Medium (32,000 – 48,000)48,000)

4040

High (over 48,000)High (over 48,000) 5151


IncomeIncomeCars / Cars /

HouseholdHousehold

00 11 2 +2 +

LowLow 5454 4242 44

MediumMedium 44 5858 3838

HighHigh 22 3030 6868

Percentage of Households in Each Income Category Versus Auto

Ownership


IncomeIncomeAutos / Autos /

HouseholdHousehold

00 11 2 +2 +

LowLow 11 66 77

MediumMedium 22 88 1313

HighHigh 33 1111 1515

Number of Trips per Household per Day


Pgh = number of trips per day generated by householders with income level g and auto ownership h

HH = number of householdsIg = Percentage of households with income level gAgh = Percentage of household in income level g

with h autos per household(PH)gh = Number of trips per day produced in

household at income level g and auto ownership h

Pgh=HH X Ig X Agh X (PH)gh


Income, # of AutosIncome, # of Autos TripsTrips Total by Total by GroupGroup

L, 0L, 0 33

1919L, 1L, 1 1414

L, 2+L, 2+ 22

M, 0M, 0 22

232232M, 1M, 1 111111

M, 2+M, 2+ 119119

H, 0H, 0 22

415415H, 1H, 1 101101

H, 2+H, 2+ 312312

Number of Trips per Day Generated

Trip GenerationRates Based on Activity (Attraction Rates)

AttractioAttractions per ns per

HouseholHouseholdd

AttractioAttractions perns per

Non-Non-Retail Retail

EmployeEmployeee

Attractions Attractions per per

Downtown Downtown Retail Retail

EmployeeEmployee

AttractioAttractions per ns per Other Other Retail Retail

EmployeEmployeee

HBHBWW

---- 1.71.7 1.71.7 1.71.7

HBOHBO 1.01.0 2.02.0 5.05.0 10.010.0

NHBNHB 1.01.0 1.01.0 3.03.0 5.05.0

Trip Attraction ExampleEmployed at a downtown commercial

center are 220 retail and 650 non-retail workers. Determine the number of trips per day attracted to this zone.

Process by which trips generated in one zone are allocated to other zones

Trip Distribution

Basic MethodsGravity Models

Growth Factor

Trip Distribution

Trip Distribution

A study area consist of three zones. Assume Kij is the same for all zones.

Trip Distribution Example

Trip Productions and Trip Productions and AttractionsAttractions

ZoneZone 11 22 33 TotaTotall

ProductioProductionsns

140140 330330 280280 750750

AttractionAttractionss

300300 270270 180180 750750Travel Time Between Travel Time Between

ZonesZones

ZonZonee

11 22 33

11 55 22 33

22 22 66 66

33 33 66 55


Time (min)Time (min) FF11 828222 525233 505044 414155 393966 262677 202088 1313

Travel Time Versus Friction FactorTravel Time Versus Friction Factor


ZoneZone 11 22 33 PP

11 4747 5757 3636 140140

22 188188 8585 5757 330330

33 144144 6868 6868 280280

Computed Computed AA

379379 210210 161161 750750

Given AGiven A 300300 270270 180180 750750

Zone to Zone Trips: First Iteration


Ajk = Adjusted attraction factor for zone j, iteration k

Cjk = Actual attraction total for zone j, iteration k

Aj = Desired attraction total for attraction zone j


ZoneZone 11 22 33 PP

11 3434 6868 3838 140140

22 153153 112112 6565 330330

33 116116 8888 7676 280280

Computed Computed AA

303303 268268 179179 750750

Given AGiven A 300300 270270 180180 750750

Zone to Zone Trips: Second Iteration

Trip DistributionGrowth Factor Model

Tij = number of trips estimated from zone i to zone jti = present trip generation in zone iGx = growth factor of zone xTi = tiGi = future trip generation in zone itix = number of trips between zone i and other

zones xtij = present trips between zone i and zones jGj = growth factor of zone j

A study area consists of four zones. The number of trips between each zone and growth factor for 5 years is shown. Determine the number of trips between each zone for future conditions.


ZonZonee

Present Trip Present Trip Generation Generation (trips/day)(trips/day)

Growth Growth FactorFactor

Trip Generation Trip Generation in 5 yearsin 5 years

AA 600600 1.21.2 720720

BB 700700 1.11.1 770770

CC 700700 1.41.4 980980

DD 400400 1.31.3 520520


ZonZonee

AA BB CC DD

AA ---- 400400 100100 100100

BB 400400 ---- 300300 ----

CC 100100 300300 ---- 300300

DD 100100 ---- 300300 ----

TotaTotall

600600 700700 700700 400400

Present Trips Between Zones


ZoneZone AA BB CC DD Estimated Estimated Total Trip Total Trip

GenerationGeneration

Actual Actual Trip Trip

GeneratiGenerationon

AA ---- 428428 141141 124124 693693 720720

BB 424288

---- 372372 ---- 800800 770770

CC 141411

372372 ---- 430430 943943 980980

DD 121244

---- 430430 ---- 554554 520520

TotalsTotals 696933

800800 943943 554554

First Estimate of Trips Between Zones

Process to determine the number (or percentage) of trips between zones that are made by various modes (auto, carpool, transit, bike/walk)

Mode Choice

Mode Choice

Determine the number of transit trips per day in a zone which has 5000 people living on 50 acres. The auto ownership is 40% with zero autos per household and 60% with one auto per household.

Mode Choice Example

Process to determine the actual routes that travelers will use

Traffic Assignment

Basic MethodsDiversion CurvesMinimum Time PathMinimum Time Path with Capacity Restraint

Traffic Assignment

Traffic Assignment

Dr. Lina Shbeeb 53

linktheonCapacityC

timetravelflowfreeT

VflowtrafficassignedforlinktheontimetravelT

where

C

VTT

0

1

4

01 15.01

demand forecasting 2008

Documents

average number of trips

travel demandlocation

travel behavior

trips producedincome

equal trips

trip generation exampletrips

following relationship

trip end production