FORECASTING TRAVEL

URBAN TRANSPORTATION FORECASTING PROCESS

1. Data Collection (or inventories)

2. Analysis of existing conditions and calibration of forecasting techniques

3. Forecast of future travel demand

4. Analysis of Results

TAZ

traffic analysis zones

DATA COLLECTION

provides information about the city and its people that will serve as the basis for developing travel demand estimates

The data includes information about:

economic activity (employment, sales volume, income, etc.)

land use (type, intensity)

travel characteristics (trip and traveler profile)

transportation facilities (capacity, travel speed, etc)

surveys and previously collected data

POPULATION AND ECONOMIC DATA

These are allocated to the study area, and the totals are distributed to each zone.

This process can be accomplished by using either a ratio technique or small-area land-use allocation models.

TRANSPORTATION INVENTORIES

A computerized network of the existing street and highway system is produced. The network consists of a series of links, nodes, and centroids.

Links

portion of a highway system described by its capacity, lane width, and speed

Node

the start/endpoints of a link; represents an intersection or location where a link changes direction, capacity, width or speed.

Centroid

location within a zone where trips are considered to begin and end

External Stations

• Established at the study area boundary

• External stations are those roadways where traffic is likely to enter or exit the study area, such as primary and interstate facilities

• Are used to account for the impact of changes outside the study area on the travel network within the study area

Transportation facility inventories

provide the basis for establishing the networks that will be studied to determine present and future traffic flows.

GIS

spatially-oriented database management processing system containing location and attribute information for manmade and natural features and supporting related queries with these features.

TRAVEL SURVEYS

are conducted to establish a complete understanding of the travel patterns within the study area.

O-D Surveys (Origin-Destination Surveys)

• Used to understand why people travel and where they wish to go to

• Asks questions about each trip that is made on a specific day

CALIBRATION

is concerned with establishing mathematical relationships that can be used to estimate future travel demand.

Travel forecasts are made by applying the relationships developed in the _________ process.

STEPS IN THE TRAVEL FORECASTING PROCESS

• Step 1: Population and Economic Analysis

• Step 2: Land Use Analysis

• Step 3. Trip Generation

• Step 4. Trip Distribution

• Step 5. Modal split

• Step 6. Traffic Assignment