Ed HardEd Hard

Stephen FarnsworthStephen Farnsworth

David Pearson David Pearson

Methods for Conducting O-D Travel Surveys on

High Volume (HV) Facilities

11th Conference on Transportation Planning Applications

May 7, 2007

The inability to conduct ‘intercept’ travel surveys on high volume facilities means loss of key data needed for local planning and travel models.

Problem: Collecting Survey Data Problem: Collecting Survey Data on High Volume Facilitieson High Volume Facilities

External Surveys and HV SitesExternal Surveys and HV Sites

M PO B oundary

Network

Intercept Survey Location

High Volum e Survey Location

Conducted around periphery of Conducted around periphery of urban areasurban areas

HV sites carry majority of traffic HV sites carry majority of traffic into/out of areainto/out of area

Example: 2005 Dallas SurveyExample: 2005 Dallas Survey• 93 external stations93 external stations• 9 of 93 were HV9 of 93 were HV• 9 HV sites carried 52% of traffic9 HV sites carried 52% of traffic

Traditional Intercept MethodTraditional Intercept Method

ComputerTablets

Traffic Control Plans

License Capture License Capture MethodsMethods

Match or MailoutMatch or Mailout Plates recorded byPlates recorded by

• Video camcordersVideo camcorders• High-speed camerasHigh-speed cameras• Voice recordersVoice recorders• Manually with ‘observers’ Manually with ‘observers’ and ‘recorders’and ‘recorders’

Categories of HV Survey Categories of HV Survey MethodsMethods

Intercept InterviewIntercept Interview Intercept Postcard MailbackIntercept Postcard Mailback License MatchLicense Match License MailoutLicense Mailout

Data Elements Collected Data Elements Collected Intercept vs. License Methods Intercept vs. License Methods

Data ElementData Element InterceptIntercept License License MatchMatch

LicenseLicense

MailoutMailout

Local vs. ThruLocal vs. Thru Trip O&DTrip O&D XX ResidencyResidency XX Veh. OccupancyVeh. Occupancy XX Trip PurposeTrip Purpose XX Trip LengthTrip Length XX Trip FrequencyTrip Frequency XX

Select Example Across USSelect Example Across US

External SurveyExternal Survey HV Survey Method UsedHV Survey Method Used1. Texas DOT1. Texas DOT License Mailout and License MatchLicense Mailout and License Match

2. Tampa, FL2. Tampa, FL License MailoutLicense Mailout

3. Denver, CO3. Denver, CO Intercepts on Freeway Off RampsIntercepts on Freeway Off Ramps

4. Philadelphia, PA4. Philadelphia, PA Intercepts on Shoulders of FreewayIntercepts on Shoulders of Freeway

5. Ohio, DOT5. Ohio, DOT License Mailout and InterceptsLicense Mailout and Intercepts

6. Phoenix, AZ6. Phoenix, AZ Intercepts at Ramps/InterchangesIntercepts at Ramps/Interchanges

7. Los Angeles, CA7. Los Angeles, CA License MailoutLicense Mailout

8. Raleigh, NC8. Raleigh, NC License Match, Rest Area Intercepts License Match, Rest Area Intercepts

9. Little Rock, AR9. Little Rock, AR License MailoutLicense Mailout

10. Chattanooga, TN10. Chattanooga, TN Mailback at Ramps / InterchangesMailback at Ramps / Interchanges

Factors Considered in Selecting Factors Considered in Selecting HV MethodHV Method

Roadway cross-section, physical conditionsRoadway cross-section, physical conditions Policies of DOT, affected agenciesPolicies of DOT, affected agencies Level of traffic (AADT)Level of traffic (AADT) Data elements and qualityData elements and quality Costs and resources availableCosts and resources available Potential for negative feedbackPotential for negative feedback

Intercept Interview MethodIntercept Interview Method

Limited use in HV externals. Limited use in HV externals. Used more in toll feasibility,Used more in toll feasibility, user / attitudinal studiesuser / attitudinal studies Use along HV facilities:Use along HV facilities:

• At / near ramps or tollsAt / near ramps or tolls• On shoulders along interstate (one case)On shoulders along interstate (one case)• At weigh stations, rest areas, truck stops for commercial vehicles / trucksAt weigh stations, rest areas, truck stops for commercial vehicles / trucks

External Surveys: Philadelphia (2001) Phoenix (1999), Denver (1998)External Surveys: Philadelphia (2001) Phoenix (1999), Denver (1998)

Intercept InterviewIntercept Interview

PROsPROs CONsCONs Data qualityData quality Response rateResponse rate All data elements All data elements collectedcollected Control of samplingControl of sampling Ability to follow-upAbility to follow-up Data available soonerData available sooner

SafetySafety Stopping vehiclesStopping vehicles Agency coordinationAgency coordination TCP and permit TCP and permit approvalsapprovals Dependent on law Dependent on law enforcementenforcement Negative press / PRNegative press / PR

Intercept Postcard Mailback Intercept Postcard Mailback MethodMethod

Postcard handout in lieu of interviewPostcard handout in lieu of interview Limited use in externals, more in Limited use in externals, more in

corridor or user / attitudinal studiescorridor or user / attitudinal studies Used on / near freeway ramps, toll plazasUsed on / near freeway ramps, toll plazas 2002 Chattanoonga, TN external2002 Chattanoonga, TN external

Intercept Postcard MailbackIntercept Postcard Mailback

PROsPROs CONsCONs Less disruptionLess disruption Traffic delays shorterTraffic delays shorter Most data elements Most data elements collectedcollected Cost < interceptCost < intercept

SafetySafety Stopping vehiclesStopping vehicles Self selection bias Self selection bias Lower response rateLower response rate TCP and permit TCP and permit approvalsapprovals Dependent on law Dependent on law enforcementenforcement

Video License CaptureVideo License Capture

High-speed, specification High-speed, specification camcorders usedcamcorders used

Rear license plates Rear license plates recordedrecorded

Info needed: plate #, state, Info needed: plate #, state, time, directiontime, direction

Camera’s on overpass or Camera’s on overpass or shouldershoulder

Used in majority of match / mailout surveysUsed in majority of match / mailout surveys

License Match MethodLicense Match Method

Plates matched between HV sitesPlates matched between HV sites All HV sites recorded on same All HV sites recorded on same

dayday Used to estimate percent I-E and Used to estimate percent I-E and

E-E trips (local vs. thru E-E trips (local vs. thru movements)movements)

Travel time runs neededTravel time runs needed

M PO B oundary

Network

Intercept Survey Location

High Volum e Survey Location

License MatchLicense Match

PROsPROs CONsCONs SafetySafety No traffic disruptionNo traffic disruption No TCP requiredNo TCP required No use of state DMV No use of state DMV recordsrecords

Limited dataLimited data All sites must be All sites must be recorded on samerecorded on same dayday

Surveys Using License MatchSurveys Using License Match

2006 San Antonio / Austin External2006 San Antonio / Austin External• 8 HV sites requiring 34 video cameras8 HV sites requiring 34 video cameras• 42 intercept sites42 intercept sites

2006 Dallas-Ft. Worth External2006 Dallas-Ft. Worth External• 9 HV sites requiring 36 video cameras9 HV sites requiring 36 video cameras• 34 intercept sites34 intercept sites

2001 Metrolina Region External2001 Metrolina Region External• 43 video cameras43 video cameras

License Mailout MethodLicense Mailout Method

Most common method for HV sites in Most common method for HV sites in externalsexternals

Same as ‘match,’ but plates queried Same as ‘match,’ but plates queried against state DMV records and surveys against state DMV records and surveys mailedmailed

Used for non-commercial vehicles onlyUsed for non-commercial vehicles only Mailout includes info on survey purpose, Mailout includes info on survey purpose,

assurance for anonymity, toll free #, etc.assurance for anonymity, toll free #, etc.

License MailoutLicense Mailout

PROsPROs CONsCONs SafetySafety No traffic delay or No traffic delay or disruptiondisruption No TCP requiredNo TCP required Most data elements Most data elements collectedcollected

Data qualityData quality Use of DMV recordsUse of DMV records Quick turn-around Quick turn-around needed betweenneeded between capture and mailout capture and mailout Out-of-state platesOut-of-state plates Negative PR, privacyNegative PR, privacy rightsrights

What Traffic Level is High Volume?What Traffic Level is High Volume?

Few agencies have HV ‘threshold’ valueFew agencies have HV ‘threshold’ value

Intercepts on freeways, interstates often Intercepts on freeways, interstates often prohibited prohibited

Queuing analyses used to determine volume Queuing analyses used to determine volume when queuing is problematic. Two when queuing is problematic. Two categories:categories:• Blocked traffic lane, 2-lane roadwaysBlocked traffic lane, 2-lane roadways• Lane reduction, 2 or more lanes in survey directionLane reduction, 2 or more lanes in survey direction

Queuing Analysis:Queuing Analysis: Blocked Lane Blocked Lane

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25

0 50 100 150 200 250 300 350

Traff ic Volume (vph)

Que

ue L

engt

h (v

ehs)

2 surveyors

3 surveyors

4 surveyors

5 surveyors

6 surveyors

7 surveyors

2 lane roadways2 lane roadways Queues correlated with Queues correlated with

traffic volumetraffic volume Number of surveyors Number of surveyors

has little affecthas little affect For TxDOT, 150-200+ For TxDOT, 150-200+

veh / hour per lane veh / hour per lane problematicproblematic

Queuing Analysis:Queuing Analysis: Lane Reduction Lane Reduction

2 or more lanes in 2 or more lanes in direction of surveydirection of survey

TCP lane reductionsTCP lane reductions Queues problematic as Queues problematic as

volumes approach volumes approach 1,000 vph1,000 vph

Analysis supports Analysis supports TxDOT policy defining TxDOT policy defining 20,000 ADT as HV20,000 ADT as HV

0

10

20

30

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0 200 400 600 800 1000 1200 1400

Traffic Volume (vph)

Que

ue L

engt

h (v

eh)

Average queue length

85th percentile of queue length

Maximum queue length

Technology in HV SurveysTechnology in HV Surveys

Current Current • Video / camcorders, hi-speed camerasVideo / camcorders, hi-speed cameras• Infrared videoInfrared video• Optical character recognition (OCR)Optical character recognition (OCR)

• Video data reduction softwareVideo data reduction software• Radio frequency ID, Toll / E-Z tagsRadio frequency ID, Toll / E-Z tags

Future potentialFuture potential• Cellular phone trackageCellular phone trackage• Vehicle telematicsVehicle telematics

License Mailout: TxDOT PracticeLicense Mailout: TxDOT Practice

Message boards used to inform publicMessage boards used to inform public

License Mailout: TxDOT PracticeLicense Mailout: TxDOT Practice Set-up on IH-10 at Texas / Louisiana borderSet-up on IH-10 at Texas / Louisiana border

March 2007March 2007

License Mailout: Lessons LearnedLicense Mailout: Lessons Learned

Keep survey form simpleKeep survey form simple Cover letter: content, tone, and appearance Cover letter: content, tone, and appearance

importantimportant Use pre-addressed, postage paid envelope or Use pre-addressed, postage paid envelope or

postcardpostcard Ensure return responses are anonymousEnsure return responses are anonymous Provide toll free numberProvide toll free number Keep accurate records of all calls receivedKeep accurate records of all calls received No more than 3-day turn-around between No more than 3-day turn-around between

capture and mailoutcapture and mailout

QUESTIONSQUESTIONS

Ed Hard (979) 845-8539 e-hard@tamu.edu