Putting the LBRS and other GIS data to Work for Traffic Flow Modeling in Erie County

Sam Granato, Ohio DOT

Carrie Whitaker, Erie County

2015 Ohio GIS ConferenceSeptember 21 - 23, 2015 | Hyatt Regency Columbus| Columbus, Ohio

What Is A Metropolitan Planning Organization?

The MPO is a transportation policy-making organization made up of representatives from local government and transportation authorities. The Federal Surface Transportation Assistance Act of 1973 requires the formation of an MPO for any urbanized area with a population greater than 50,000. Erie County was designated as an MPO in 2003 as a result of the 2000 US Census (pop 50,693)

Includes all of Erie Co. and the Lorain Co. portion of the City of Vermilion

What Is A Metropolitan Planning Organization?MPO oversees federal highway dollars (STP,

TA) by making decisions regarding project funding for the region.

MPO is also charged with short and long range transportation planning for the MPO planning area.

The Long Range Transportation Plan (LRTP) is a required document for all MPO’s.Plan must cover 20 year timeframeUpdated every 5 years (Approved July

2015)Plan emphasizes mobility and access

for people and goods, efficient system, performance/preservation, and quality of life

2040 LRTP

The LRTP Planning Process

Includes the following steps:The forecasting of future population, traffic, and employment growth;

Assessing projected land uses in the area;

Identifying major growth corridors

Traffic modeling assists us with completing these tasks and used to evaluate and develop alternative capital and operating strategies for movement of people/goods

Trendlines? – not usable for new route locations, sometimes not sufficient for significant improvements (including crossing or parallel travel routes) or when nearby land use changes.

Seasonal traffic – unlike most of the rest of the state, the local economy is driven considerably by summer recreation, but the impact varies by location within Eric county. So separate models created by season (and weekday vs weekend in summertime).

Other unique features of travel demand modeling – dynamic travel routing (for duration as well as extent of congestion), including use of travel time variability as well as average values.

The rationale for a formal traffic forecasting process, and why the one for Erie RPC is unique:

1) Select subset of digital road and traffic control shape files (LBRS) and create a routable network

2) Divide area into zones based on access to the selected network, and geocode land use data to these zones

3) Develop trip generation by zone and trip purpose/vehicle type

4) Allocate daily trip totals by purpose and direction into 15-60 minute time intervals

5) Develop trip-length distributions and select destinations for all trips by purpose

6) Assign traffic to network by 15-60 minute time period (iterative w/#5)

The (iterative) model process:

Roadway centerline files, old and new: (improved spatial accuracy for both visualization and

improve integration with other data sources)

LBRS (digital e-911) centerline and supplemental files

ODOT Road Inventory/OSIP aerials/pictometry

State & local traffic counts and travel speed/time data

Highway capacity/level of service relationships

Source material: (roadway network)

Shape files available thru the LBRS program

(For traffic modeling, most of the LBRS file’s value is in the location, topology, connectivity and visualization - most data is overlayed from other sources.)

Use of RR crossing file with train data and queuing delay estimates allows analysis of traffic re-routing

(Use of stop/yield (small dots) and local speed limit sign inventories also eliminates need for “rule-based” systems

Census data for population characteristicsVarious employment/worker/school data filesITE & related Trip Generation manualsNCHRP research reports for guidance on

segmenting demand by trip purpose, vehicle type, and time of day

Source material, cont. (land use and demand)

Base year results (traffic volumes)

30 300 3000 3000030

300

3000

30000

ERPC 2010 BASE YEAR MODEL (summer weekdays)

COUNTED AADT (DIRECTIONAL) - BLUE LINES REPRESENT AVERAGE COUNT ERROR (FHWA REPORT)

MODELED AADT(BY DI-

RECTION)

20 200 2000 2000020

200

2000

20000

ERPC 2010 BASE YEAR MODEL (spring/fall weekdays)

COUNTED AADT (DIRECTIONAL) - BLUE LINES REP-RESENT AVERAGE COUNT ERROR (FHWA REPORT)

MODELED AADT(BY DI-

RECTION)

Varies by level of aggregation, but data sources verify that modeled travel times are generally correct (especially important for arterial congestion analysis)

Base year results (travel times)

Forecasting future land use: overall levels

ODOD forecasts of population by 5-year age and sex cohorts (combined with historical trends to forecast persons and vehicles per housing unit, along with schoolkids and resident workforce via workforce participation rates by age and sex)

ISAM-based growth rates of employment by industrial category (used in statewide model, with trendlines adjusted for recent local declines in auto industry and ODOD’s forecasted decline in schoolage children to provide “reasonable” match to population trends)

Forecasting future land use: by location

Local development plans on fileLand Use categories for vacant land (by

parcel)

Formulas for distribution of acreage for new land development – by land use type

Many different ways to analyze and present the forecasts (and trade-offs) – impact over a full day, duration vs peak intensity of congestion, other . . .

Forecasting future volumes and delays:

Alternate measure – average or change in delay over a full day instead of peak LOS

Sam.Granato@dot.ohio.govCWhitaker@eriecounty.oh.gov

Questions?