8.0 I-35W SOUTH USER TELEPHONE SURVEYS

8.1 Purpose and Approach

This telephone survey would be conducted of users of I-35W South. MnPASS users and transit riders and carpoolers are targeted in the surveys discussed previously. This survey will focus on travelers in the I-35W general-purpose freeway lanes, carpoolers using the MnPASS HOT lanes, and obtaining additional information. The survey would use the same approach Mn/DOT uses in the Perception Tracking and Omnibus surveys, but would focus specifically on the I-35W South corridor. This section outlines a modified sampling protocol and the preliminary questionnaire. The sampling plan and questionnaire will be finalized based on additional discussions among Mn/DOT, the Metropolitan Council, and the Battelle team.

8.2 I-35W South Corridor Interview Protocol

The methodology for this survey would be similar to the methodology employed by Mn/DOT for the Perception Tracking Study, with suggested modifications to address the needs of the national evaluation related to targeting specific user groups in the I-35W South corridor. The following methods are recommended for selecting the sample for the I-35W South telephone interview.

• Utilize a two-stage interview approach, with an initial short interview (2-3 questions) to screen potential respondents for travel in the I-35W South corridor. These questions will be used to target travelers who carpool in the HOT lanes and those using the general-purpose freeway lanes. Individuals will need to have traveled in the corridor before the UPA improvements and currently use the corridor. The focus of this initial screening interview would be to ascertain eligibility for the extended interview (i.e., traveled on the corridor), as well as to capture 1-2 demographic characteristics that can be used to assess and mitigate any sampling bias (i.e., race/ethnicity, number of household vehicles, etc.). The extended interview would only be conducted with candidates that have been determined to be eligible based upon the screener interview.
• Utilize an address-based sample to increase the chances of reaching persons that are most likely to utilize the I-35W South corridor. With this sampling methodology, the survey methodologist can stratify the sample based upon geographic information and historical travel pattern information to target households that are likely to use the corridors of interest. Conversely, Random Digit Dial (RDD) surveys, even those that are “list-assisted,” are increasingly suffering from the portability of telephone numbers and the increasing number of households that are cell-only households. In short, the ability to target specific geographic areas using the area code or exchange information in the telephone number is becoming more and more challenging as a greater percentage of the population has “ported” or moved outside their original telephone coverage area, but have retained their telephone number. The use of an address-based sampling methodology does not preclude the use of telephone interviews to collect information from respondents as 85 percent of address samples can be reverse-matched to a name and 60 percent can be reversed-matched to a landline telephone number.
• Employ a multi-mode survey. Recent research has found that multi-modal surveys are effective in reaching populations that cannot be otherwise reached through traditional landline telephone surveys. In particular, technology-savvy young adults are increasingly moving towards a cell-only household. Incorporating these respondents in the survey is important as they typically are technology users, and may be more prone to changing travel behavior as a result of technology deployments. A mail-out/mail-back questionnaire is recommended together with the telephone interviews to capture this group of people as well as households where a landline telephone number cannot be reversed matched.

8.3 Interview Questions

The following questions are recommended for inclusion in the telephone interviews. Many of the questions are the same as those included in the MnPASS user surveys, the on-board ridership survey, and the carpool survey. The final wording, sequencing of questions, and format for the interviews will be determined by the market research firm, in consultation with Mn/DOT, the Metropolitan Council, and Battelle team representatives.

Questions for users of the I-35W South general-purpose freeway lanes.

#	Question
3.	Approximately how many total one-way trips per week do you take on I-35W, including trips taken on the I-35W MnPASS toll lanes? _____ None _____ Less than one trip per week _____ One or two trips per week _____ Three trips per week _____ Four trips per week _____ Five trips per week _____ Six trips per week _____ More than six trips per week
4.	Approximately how many one-way trips per week do you take on just the I-35W general purpose freeway lanes? _____ None _____ Less than one trip per week _____ One or two trips per week _____ Three trips per week _____ Four trips per week _____ Five trips per week _____ Six trips per week _____ More than Six trips per week
5.	Do you use the I-35W general-purpose freeway lanes primarily for (check all that apply): _____ Work trips _____ School trips _____ Personal business _____ Work appointments _____ Recreational _____ Medical _____ Other (please specify ________________________________________________)
6.	What segments of the I-35W general-purpose freeway lanes do you normally use (check all that apply). _____ Highway 13 to I-494 _____ Highway 13 to downtown Minneapolis _____ I-494 to Highway 13 _____ Other
7.	Which factors influence your use of the I-35W general-purpose freeway lanes rather than the MnPASS lanes, riding the bus, or carpooling? (check all that apply): _____ Need car for work trips _____ Need to drop off/pick up other family member _____ MnPASS too expensive _____ Traffic congestion is not bad enough to use other modes _____ No current bus service _____ Other (Please specific________________________________________________)
8.	Do you ever ride the bus in the I-35W corridor? _____ Yes _____ No
	If yes, how frequently do you ride the bus? _____ Once a week _____ Once or twice a month _____ Once or twice a year _____ Others (Please specify _______________________________________________)
9.	Do you ever carpool in the I-35W MnPASS HOT lane from ____? _____ Yes _____ No
	If yes, how frequently do you carpool? _____ Once a week _____ Once or twice a month _____ Once or twice a year _____ Others (Please specify _______________________________________________)
10.	10. Do you ever use the I-35W MnPASS HOT lanes as a toll paying customer? _____ Yes _____ No
	If yes, how frequently do you use the MnPASS HOT lanes as a toll paying customer? _____ Once a week _____ Once or twice a month _____ Once or twice a year _____ Others (Please specify _______________________________________________)

Questions for carpoolers.

#	Question
11.	How long have you been carpooling on I-35W? _____ Less than 1 month _____ 1 to 3 months _____ 3 to 6 months _____ 6 months to 1 year _____ 1 to 2 years _____ 2 to 3 years _____ Over 3 years
12.	How often do you carpool for free on the I-35W MnPASS toll lane? _____ Once a week _____ 2 times a week _____ 5 times a week _____ Once or twice a month
13.	Who do you carpool with? _____ Family members _____ Neighbors _____ Co-workers _____ Co-students _____ Others (Please specify _______________________________________________)
14.	What is the purpose of your trip? _____ Work _____ School _____ Personal business _____ Social/entertainment _____ Medical _____ Other (please specify ________________________________________________)
15.	What segments of the I-35W MnPASS lanes do you normally use when carpooling? (check all that apply) _____ Northbound/Southbound from Highway 13 to Highway 62 _____ Northbound from Highway 62 to downtown Minneapolis _____ Northbound from 42nd Street to downtown Minneapolis _____ Northbound from I-494 to Highway 13
16.	How did you make this trip before you started carpooling on I-35W? _____ Drove alone in I-35W general-purpose freeway lanes _____ Drove alone on another freeway or roadway _____ Carpooled in the I-35W HOV lanes _____ Rode the bus on I-35W or other roadway _____ Drove alone in the I-35W HOV lanes _____ Did not make the trip _____ Other (please specify ________________________________________________)
17.	What motivated you to begin carpooling? ________________________________________________________________________
18.	Which factors influence you to carpool in the I-35W MnPASS toll lanes? (check all that apply) _____ Congestion levels in freeway lanes _____ Faster travel time _____ Improved trip-time reliability _____ Other (Please specific________________________________________________)
19.	In your opinion, what are the best things about carpooling in the I-35W MnPASS toll lanes? ________________________________________________________________________
20.	About how much time do you think you save per one-way trip during morning rush hour when you carpool in the I-35W MnPASS toll lane? _____ Minutes
21.	About how much time do you think you save per one-way trip during the afternoon rush hour when you carpool in the I-35W MnPASS toll lane? _____ Minutes
22.	Are you a MnPASS toll customer with an active toll transponder? _____ Yes _____ No
	If yes, how frequently do you use the I-35W MnPASS toll lanes as a solo driver? _____ One day per week _____ Two or three days per week _____ More than three days per week _____ One or two days per month
23.	Do you ever ride the bus on I-35W? _____ Yes _____ No
	If yes, how frequently do you ride the bus on I-35W? _____ One day per week _____ Two or three days per week _____ More than three days per week _____ One or two days per month
24.	Do you ever drive alone in the general-purpose freeway lanes? _____ Yes _____ No
	If yes, how frequently do you ride the bus on I-35W? _____ One day per week _____ Two or three days per week _____ More than three days per week _____ One or two days per month

Questions for both general-purpose freeway lanes travelers and carpoolers.

8.4 Analysis Methods

The Battelle Evaluation Team would utilize this survey to determine if there has been a shift among the traveling public regarding the use of carpooling and to determine why people travel in the general-purpose freeway lanes rather than using the HOT lanes, carpooling, or riding the bus. In particular, the analysis will be conducted to characterize the extent of any shift and to statistically test whether the UPA deployment has resulted in a 5 percent increase in new car poolers (from general purpose lanes) among the population of travelers utilizing these corridors. Additional analyses will be conducted to characterize the extent and reasons for (or not) changes in carpooling in the MPASS lanes. Finally, statistical analysis will be conducted to estimate whether a significant percentage of the traveling population in the I-35W corridor perceives that there has been positive change (benefit) in traffic conditions from pre-deployment experiences.

Statistical estimation and hypothesis testing will be conducted using weighted survey responses to reduce sampling bias associated with the survey process or non-response. However, because the actual size of the population of travelers in the corridor is not known exactly, the survey weights will be constructed so that they help to mitigate these biases, but sum to the sample totals. This will be performed by creating expansion factors by population characteristics in the geographic areas targeted for the survey including age, race/ethnicity, number of household vehicles, etc. using population totals from the American Community Survey (ACS)³, and then pro-rated back to the original sample by dividing by the average weight. Statistical analysis will be performed in SAS, SUDAAN, WesVar, or another comparable statistical analysis software package that can account for the survey design. Statistical tests will be conducted using normal theory tests (t-test, F-tests, etc.) at 95 percent confidence levels.

A sample size of 1,000 completed surveys is recommended to be targeted for this survey effort, which is consistent with the industry standard for most public opinion surveys⁴. Table 8-1 summarizes the anticipated statistic power⁵ or precision associated with estimating a characteristic of interest in the sample group (e.g., percentage of respondents reporting a particular reason for not carpooling) for three different sample sizes.

8.5 Schedule and Responsibilities

It is recommended that the I-35W South user telephone interviews be conducted in September 2011, one year after all of the Minnesota UPA projects, including the HOT lanes in the Crosstown Commons section, are completed and in operation. This schedule will allow for one full year of operation with the full segment of the HOT lanes on I-35W South. Mn/DOT or the Metropolitan Council would be responsible for conducting the interviews. It is anticipated that a market research firm would be used to conduct the interviews. This firm would finalize the sample methodology and survey instrument, in consultation with Mn/DOT, the Metropolitan Council, and the Battelle team. The firm would also conduct the interviews and provide a report on the results and an electronic file with the complete results. Members of the Battelle team will analyze the results and will incorporate the results into the final report.

³ Information can be found at the American Community Survey Website: http://www.census.gov/acs/www/.
⁴ American Association for Public Opinion Research, http://www.aapor.org/Margin_of_Sampling_Error.htm
⁵ Statistical power refers to the ability of the hypothesis test to correctly identify a significant difference when one exists. Typically, statistical power of 80% or more is considered to be "reasonable."