Chittenden County Land Use -

Transportation Decision Support

System

http://www.ccmpo.org/planning/dss

November 19, 2003

Chittenden County Metropolitan Planning OrganizationChittenden County Regional Planning Commission

Vermont Agency of Transportation

Presentation Overview

• Why use the DSS?

• Use of DSS within Planning Processes

• Structure of Decision Support System (DSS) Software

• Current Test Results

What is the Land Use-Transportation

Decision Support System (DSS)?• A free-standing, GIS-embedded software

that examines the interrelationships of transportation and land use, and provides outputs in support of local and regional planning processes.

• The outputs have been designed to assist stakeholders and decision-makers in:

1. Assessing Existing Conditions2. Creating Plans3. Implementing Plans4. Achieving Plans

Why DSS?

• Better integration of transportation model with more detailed land use modeling capabilities.

• Tool for examining influences of large “regionally significant” projects.

• Visual and quantitative information to assist policy boards in making decisions.

• Output informs planning process.

Step #1 Identify Values

Step #5Develop

Alternative Plans

Step #2Determine Indicators

Step #4Evaluate

Current Conditions

Step #6Evaluate

Alternative Plans

Step #3Develop

Assumptions

Step #7Adopt Desired

Plan

In Support of Planning

DSS Software Overview

• Snapshot Mode– Parcel Based

• Forecast Mode– Resizable Grid

(50-200 acres)

200 acre grid

Snapshot results screen

“Snapshot” Analysis

• Static, Parcel based analysis• Useful in examining specific

development proposals• Does not automatically forecast future

development • Training for Local Planners completed

on July 24, 2002• Pilot studies ongoing in Shelburne and

Charlotte

Forecast Analysis

• Forecasts location of future housing and employment and associated travel demand

• Useful in examining projects with Regional Impacts

Required Inputs for DSS Forecast Mode

Environm ental Constraints(septic suitability, steep slopes,

wetlands, etc.)

Existing Housing andEm ploym ent

DecisionSupportSystem

Software

Ind icators Transportation

Dem and Housing and

Em ploym entG rowthA llocations

M aps of"A ttractiveness"

Regional Projections of HousingDem and and Em ploym ent

Growth

Land Use Scenario(perm itted land uses, allowable

densities, etc)

Municipal andTransportation Infrastructure

Changes

Existing Conditions

Forecast Conditions

Existing Municpal andTransportation Infrastructure

Chittenden CountyResidential

Zoning

Chittenden CountyNon-Residential

Zoning

Forecast Accessibility

• The “Accessibility” is calculated for each grid cell

• Accessibility is an objective measurement that describes the convenience and efficiency of traveling between locations

• Accessibility is the inverse of travel time between locations factored to reflect:– The number of origins and destinations

– The grid cell’s proximity to roadways

TAZ-Level Accessibility

Smoothed TAZ-level Accessibility

Distance to Local Streets

Factored Grid-level Accessibility

Forecast Attractiveness

• The “Attractiveness” is calculated for each grid cell

• Each cell’s Accessibility measure is factored to reflect development incentives and/or disincentives

Septic Soil and Municipal Sewer Parameters

NOTE: These data reflect the 1996 on-site rules

Potential Attractiveness Factors

Municipal Sewer Service Area

105%

Conventional Septic

100%

Mound System

95%

Unsuitable 85%

Housing and Employment Allocation

• Based upon the final Attractiveness “scores”, all developable cells are grouped into 10 deciles

• The DSS then assigns 50% of the new housing and employment into first decile, 25% into second decile, 12.5% into third decile, etc.

• If a decile cannot absorb the appropriated growth, then the excess development goes into the next decile

• Within each decile, the cells are randomly chosen

DSS ForecastHypothetical Tests

Two Rounds of Testing

Round 1 4 Scenarios:• 1A - Base land use and transportation network • 1B - Increased density allowances throughout Region• 1C - Five-lane Route 7• 1D - Increased density allowances and Five-lane

Route 7

Round 2 4 Scenarios• 2A – Base land use and transportation network• 2B – Base land use and express bus service to Jericho

& new Milton interchange• 2C – TOD land use and Base transportation network• 2D – TOD land use and express bus service to Jericho

& new Milton interchange

Single-Family ResidentialHypothetical Testing Scenario 1A

Base Land Use and Base Transportation Network

Accessibility to

Employment (2024)

Hypothetical Testing Scenario 1BExtreme Land Use and Base

Transportation Network

Single-Family ResidentialHypothetical Testing Scenario 1A

Base Land Use and Base Transportation Network

Attractiveness (2024)

Hypothetical Testing Scenario 1BExtreme Land Use and Base

Transportation Network

Volume to Capacity RatioHypothetical Testing Scenario 1A

Base Land Use and Base Transportation Network

Hypothetical Testing Scenario 1BExtreme Land Use and Base

Transportation Network

Comparison of Housing Growth Allocation

Base Case vs. Extreme Scenarios

Comparison of Employment Growth Allocation

Base Case vs. Extreme Scenarios

General Conclusions

• Land use policies have a stronge influence on Accessibility and Attractiveness

• Influence of land use policies dampened by the influence of transportation improvements

• Transportation improvements in the urban/suburban core of the County create more accessibility in the Transition and Rural Planning Areas

• Existing high allowances for non-residential growth are only slightly impacted by changes to transportation system and/or land use policies

• Current land use policies can not accommodate anticipated housing demand

Steering Committee Recommendation

• Recommended to CCMPO/CCRPC Boards the DSS software is an appropriate tool to assist in local and regional land use and transportation planning processes.

Next Steps• Model development is an ongoing process.

• DSS provides better information for planning.

• DSS provides the best analysis possible to date, but will not predict an absolute future.