Sverdrup Civil, Inc. is under contract to the Arizona Department of Transportation (ADOT) as the Prime Consultant for the US 93 Location/Design Concept Study. The purpose of this study is to prepare a long-range plan for improvement of US 93 between Wickenburg and the Santa Maria River. Among the various design alternatives being considered is a bypass around Wickenburg.

An origin-destination survey was conducted, as part of the US 93 L/DC Study, in order to obtain traffic data that would be useful in analyzing the feasibility of potential bypass alignments and the overall impact the bypass might have on existing travel patterns. Roadside interviews were used to collect information on trip origin and destination, trip purpose, and other data from a selected sample of drivers. These interviews were conducted on two days – Saturday, May 1, and Thursday, May 6, 1999 – in order to identify any differences between weekday and weekend travel patterns. The survey stations were located on US 60 near MP 116, approximately five miles south of Wickenburg.

As a subconsultant to Sverdrup, Heffernan & Associates assumed overall responsibility for the origin-destination survey – designing the survey, training and supervising field personnel, and tabulating the survey results. Assisting Heffernan & Associates were two other firms – Traffic Research & Analysis, Inc. (TRA), which provided most of the survey personnel, and Barricade and Light Rental, Inc. (BLR), which provided the flaggers, traffic cones and signs.

This report describes how the roadside interviews were conducted and provides summary tables of the information collected.

A brief description of the survey design is presented in this chapter.

Survey stations were set up on US 60, in the vicinity of the rest area located at MP 116. In this area, US 60 is a four-lane divided highway with paved shoulders and carries approximately 13,000 vehicles per day.

This location, approximately five miles south of Wickenburg, was chosen in order to maximize the usefulness of the survey responses. It was far enough to the south that intercepted traffic might use either of the bypass corridors that had been identified in a previous ADOT study (see Exhibit 1). Local trips would also be minimized, since the stations were well outside the town’s commercial areas.

Since the US 93 corridor carries a substantial amount of recreational traffic, the roadside interviews were conducted on both a Saturday (May 1) and on a weekday (Thursday, May 6). Data was to have been collected for 12 hours – from 6:30 AM until 6:30 PM—on both days. However, the contractor setting up the required traffic control devices was unable to complete this task in time, and the interviewers could not safely operate the stations until all signs and cones were in place. On Saturday, May 1, the survey began at 7:30 AM. On Thursday, May 6, the surveyors were able to start slightly earlier – at 7:15 AM.

ADOT staff was asked if the survey hours could be extended beyond 6:30 PM in order to make up for the missing time. However, due to concerns about reduced visibility in the early evening, it was felt that the surveys should end at 6:30 PM as originally planned.

Only some of the vehicles passing by the survey station were chosen for interviews. Traffic cones and signs were used to slow down traffic and merge all vehicles into a single lane. A flagger then directed those drivers selected for interviews over to the roadway shoulder, while allowing all other vehicles to continue straight through. Surveyors waited for the selected vehicles to approach in a "buffer zone" created by placing traffic cones in the unused travel lane. Up to three vehicles could be accommodated for interviews at one time.

The original goal was to obtain a 10-percent sample of traffic. This was to be done by stopping three vehicles for interviews and then letting 27 vehicles pass by, before stopping three more vehicles. However, after operating the stations for a short time, it became apparent that a much larger sample could easily be obtained without jeopardizing traffic safety. As soon as the vehicles previously selected for interviews had left the survey station and merged back into traffic on US 60, the flagger would direct the next three vehicles over to the shoulder (rather than waiting for 27 vehicles to pass by before starting to select again). While these vehicles were being interviewed, all other traffic was permitted to pass by the survey station.

When it was time to direct more vehicles over to the survey station, the flagger would normally choose the next three vehicles. However, no more than one large truck (having three axles or more) was ever taken at one time in order to ensure that the selected vehicles would not exceed the storage capacity of the interview station. Also, all buses were excluded from the survey sample.

Behavior Research Center developed a draft questionnaire, which was then modified by Heffernan & Associates to make it more suitable for roadside use (where interviews have to be completed as quickly as possible). The actual survey form used when interviewing northbound (westbound) drivers is shown in Exhibit 2. A slight change in wording – "Did you stop in Wickenburg?" rather than "Will you stop in Wickenburg?" – appeared on the survey form for southbound (eastbound) drivers, but the same survey procedures were used for both directions of travel.

All drivers selected for interviews were asked these four questions:

• Where did you begin your trip?
• Where will you end this trip?
• What is the purpose of making this trip? (Most of the pre-determined choices on the survey form are self-explanatory. "Business" was checked when the driver’s response indicated non-commuter business-related travel, such as a truck driver making deliveries or a salesman calling on clients. Trips to a doctor, beauty salon, bank, etc. were marked as "personal business.")
• Do you live in Wickenburg?

Then, if the driver was not a town resident and Wickenburg had not been mentioned as the originating point or destination for the trip, the interviewer asked if the driver planned to stop in the town (northbound) or had stopped there (southbound).

If the driver indicated a stop would be made, or had been made, additional questions were asked. First, the interviewer would try to find out the primary reason for stopping in Wickenburg. Then a hypothetical scenario about the bypass would be given. The interviewer would describe the bypass and ask if the driver would still stop in Wickenburg if it took an extra 15 minutes to exit the bypass in order to reach the town. If the driver indicated the stop would no longer be made, an incremental approach was used (10 extra minutes? 5 extra minutes?) to determine the maximum increase in travel time that would be acceptable before the driver changed his or her plans to stop. The final question asked if the driver had to see the town from the bypass before deciding to stop, or if guide signs would be enough for the driver to make the decision.

After completing the interview and thanking the driver, the interviewer recorded the type of vehicle in the appropriate place on the survey form.

A vehicle classification count was also made at the same time the roadside interviews were being conducted. All vehicles passing by the survey station were counted and classified by type. This information was used to calculate the overall sampling rate, and to determine how the vehicles selected for interviews compared to the total traffic passing by the station during the survey period.

Because weekday and Saturday travel patterns were likely to be very different, results from the May 1 (Saturday) and May 6 (Thursday) surveys were analyzed separately. This chapter presents a summary of the data collected on Saturday, May 1, 1999, between the hours of 7:30 AM and 6:30 PM.

Exhibits 3 and 4 show the total number of vehicles passing by the northbound and southbound survey stations, respectively, during the time these stations were operated. Approximately 7,500 vehicles (total of both directions) were recorded during the 11-hour survey period. Over 90 percent of these vehicles were "standard" vehicles such as passenger cars, vans, pickups and other two-axle trucks. Large trucks (with three or more axles), recreational vehicles, and buses accounted for less than seven percent of the total Saturday traffic.

Although tractor-trailers (i.e., trucks having more than three axles) appear to be slightly underrepresented in the Saturday survey, interviewers failed to record the vehicle type on six percent (115) of the survey forms that day, and some of these unknown vehicles may have been large trucks.

Exhibit 5 provides a summary trip table – linking trip origins and destinations – derived from the Saturday interviews. (Data for northbound and southbound trips are presented separately in Exhibit 6.) Upon reviewing the completed survey forms, at least one trip end (origin or destination) could be identified for all but one interview, and both trip ends could be identified for over 98 percent of the interviews.

In order to make the data more meaningful, the drivers’ responses regarding trip ends were grouped into a limited number of geographic areas. These nine areas were:

• Town of Wickenburg.
• Local – Southeast includes the nearby communities of Morristown, Circle City, and Wittman. They are located along US 60, southeast of the survey stations.
• Phoenix Metro Area includes all cities, towns, and unincorporated areas located within the Phoenix urbanized area.
• US 89 Corridor includes Congress, Yarnell, Peeples Valley, Prescott, and other locations accessed by US 89.
• US 93 Corridor includes Wikieup, Kingman, Bullhead City, Laughlin (NV), Las Vegas (NV), and other places located to the north of Wickenburg, for which US 93 is the major access route.
• US 60 Corridor includes all communities along US 60 west of Wickenburg, such as Aguila, Salome, Quartzite, and Blythe (CA).
• Tucson Area includes the city of Tucson and nearby communities such as Marana, Oro Valley, and Green Valley.
• Other Arizona includes any place within Arizona that is not already included in one of the categories identified above.
• Other Non-Arizona includes all locations outside the state that are not already included in a previous category.

Local residents accounted for 21 percent of all drivers responding to the question about residency:

Approximately 29 percent (404) of the identified non-residents indicated that their trip began or would end in Wickenburg. Over 56 percent of these trips were for "personal business" or "social/recreation" purposes, as shown in the table at the top of page 15.

Over half of the through trips had "social/recreation" reported as their trip purpose. This is roughly ten percent higher than the percentage reported by all drivers interviewed that day. The through trips also had proportionately fewer home-to-work trips and shopping trips, as shown in the following table:

Exhibit 8 presents information about the trip origins and destinations reported by drivers of the through trips. Roughly 47 percent (465 drivers) indicated that the trip would have both its origin and destination within the state. The remaining 53 percent reported that at least one end of the trip (origin, destination, or both) would occur outside Arizona. The most frequently named locations outside the state were Nevada (cited in 314 interviews), California (32), and Utah (21).

In order to get an estimate of the amount of through traffic that might use a potential bypass route, drivers were asked if they had made (or were planning to make) a stop in Wickenburg. Of the 971 drivers responding to this question, 455 (47 percent) indicated a stop was made, and 516 (53 percent) indicated they traveled through the town without stopping.

Obtaining food and/or gas were the most frequently cited reasons for stopping in Wickenburg; these two items accounted for approximately 85 percent of the driver responses. The remaining 15 percent fell into the "other" category, with 21 drivers (5 percent of the total responses for this question) specifically mentioning a need to use restroom facilities as the reason for stopping in Wickenburg:

Drivers who indicated they had stopped (or planned to stop) in Wickenburg were asked two additional questions. The first question attempted to determine the maximum increase in travel time the driver would be willing to accept before deciding not to stop in Wickenburg, in the event a bypass route around the town was constructed. Drivers’ responses to this question are summarized in the following table:

One-third (147) of the drivers said they would not go into town at all if the bypass were built, but nearly two-thirds (288) indicated that they would continue to stop in Wickenburg even if doing so would increase their travel time. However, the responses (shown at the top of page 18) indicate that the longer the detour, the fewer drivers still willing to stop in town.

When answering this question, many drivers commented that their answer might vary from day to day, depending upon how badly they needed to stop for food or gas on that particular trip. As most of them noted, there are only limited opportunities for obtaining services along US 93 or US 60 other than Wickenburg. Some drivers also noted that their response would change if similar services were available along the bypass route.

The final interview question also dealt with the potential impact of a bypass on Wickenburg businesses. Of those drivers who indicated that they would continue to stop in Wickenburg even if a bypass were built, only 49 drivers indicated that they wanted to be able to see the town from the bypass; this represents just 18 percent of the total drivers answering this question. The vast majority (230 drivers, or 82 percent) said that directional signs on the bypass would be sufficient.

In this chapter, summary tables of data collected on Thursday, May 6, 1999, are presented. Major differences between these data and the data obtained on the preceding Saturday (May 1) are also noted where appropriate.

On Thursday, May 6, the interviewing began at 7:15 AM and ended at 6:30 PM. During that time, approximately 7,500 vehicles (total of both directions) passed by the survey stations – roughly the same total volume as was observed during a similar time period on Saturday. Exhibit 9 presents the results of the vehicle classification count conducted at the northbound survey station on Thursday; Exhibit 10 provides similar data for the southbound station.

The vehicle mix recorded on Thursday was significantly different from the mix recorded on Saturday. Large trucks (with three or more axles), recreational vehicles, and buses accounted for nearly 12 percent of the total traffic on Thursday – but less than seven percent on Saturday. There were nearly twice as many large trucks observed on Thursday than on Saturday.

The following table shows the trip purposes reported by drivers interviewed on Thursday:

Approximately 45 percent of all drivers responding to this question reported that the trip was work-related. On Saturday, only 21 percent of the interviews involved commuting to/from work or other business travel. Conversely, significantly fewer drivers reported the trip was "social/recreation" in nature (25 percent) on Thursday than had given this reponse on Saturday (40 percent).

A summary trip table – linking trip origins and destinations – was derived from the Thursday interviews; this is presented in Exhibit 11. Both trip ends could be identified for all but 15 interviews. Exhibit 12 shows separate trip data for northbound and southbound trips.

Exhibit 13 provides the same data as Exhibit 11, but expresses the information in terms of the percentage of total trips. A comparison of this trip table with Exhibit 7 (the equivalent table for Saturday) shows that the distribution of trip origins and destinations was essentially the same on both survey days.

Approximately 31 percent of the identified non-residents indicated that their trip began or would end in Wickenburg – accounting for a total of 473 trips. On Saturday, most of these trips to and from the town were for "personal business" or "social/recreation" reasons. However, on Thursday, more than half of the trips to or from Wickenburg fell into the categories of "to/from work" or "business" trips, as shown in the following table:

The remaining 69 percent of the non-residents interviewed (1,034 drivers) were traveling through the town on their way somewhere else.

Of the total sample collected on Thursday, 1,041 interviews were associated with through trips – i.e., trips having neither an origin nor destination in Wickenburg. This represents 53 percent of the total interviews obtained that day. Through trips comprised a similar proportion (56 percent) of all trips on Saturday.

The percentage of through trips was similar for both northbound and southbound trips, as shown in the following table:

The percentage of through trips with "social/recreation" reported as the trip purpose was significantly higher than the percentage of total trips with the same purpose. The through trips also had proportionately fewer home-to-work trips and shopping trips, as shown in the following table:

This same pattern was observed in the analysis of data collected during the Saturday interviews.

Exhibit 14 presents information about the trip origins and destinations reported by drivers of the through trips. Approximately 43 percent of the through trips (449 interviews) had both an origin and destination within Arizona. The remaining 57 percent reported that at least one end of the trip (origin, destination, or both) was located outside the state. The most frequently named out-of-state locations were Nevada (493 mentions), California (46), and Utah (13); these same locations were also named most often during the Saturday interviews.

When drivers indicated that their trip did not start or stop in Wickenburg, they were asked if they had made (or were planning to make) a stop in Wickenburg. Approximately 45 percent (460 drivers) of the total drivers responding to this question (1,029) indicated they would stop in the town. The remaining 55 percent (569 drivers) indicated that they would not. On Saturday, a similar percentage (47 percent) made a stop in Wickenburg.

Approximately 85 percent of the drivers who stopped in Wickenburg did so to get food and/or gas. The remaining 15 percent indicated "other" reasons for stopping, with several noting a need to use restroom facilities or to just "take a break from driving."

Drivers who indicated they stopped in Wickenburg were asked if they would still have stopped if there were a bypass route around the town. The following table summarizes drivers’ responses to the maximum increase in travel time they would be willing to accept before deciding not to stop in Wickenburg:

Again, the percentage of drivers that would continue to stop in Wickenburg was dependent upon the amount of time it would take to get into town from the bypass:

In general, drivers interviewed on Thursday were somewhat more willing to accept increased travel times than drivers interviewed on Saturday. Nearly 72 percent of the drivers asked this question on Thursday were willing to add five minutes more onto their travel time to stop in the town; the corresponding percentage on Saturday was only 66 percent. The percentage of drivers who would no longer stop in the town if the bypass were built was higher on Saturday (34 percent) than on Thursday (28 percent).

Many of the drivers interviewed on Thursday indicated that their answer to this question depended upon how badly they needed to stop for food or gas on a particular trip, since there were not many places they could obtain services along US 93 or US 60 other than Wickenburg. This also happened on Saturday.

Of those drivers who indicated that they would continue to stop in Wickenburg even if a bypass were built, only 52 drivers (17 percent of the total drivers answering this question) indicated that they wanted to be able to see the town from the bypass. The other 262 drivers (83 percent) said that directional signs on the bypass would be all that was needed to guide them into Wickenburg.

Survey stations were operated on Saturday, May 1, and Thursday, May 6, 1999. Over 3,700 usable interviews were obtained; this represents approximately 25% of all vehicles passing by the survey stations.

The following statistics were derived from the total responses for each survey question, using the composite data from both survey days: