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OCR for page 16
16 Guidebook for Conducting Airport User Surveys Table 2-1. Advantages and disadvantages of each survey method. Survey Method Advantages Disadvantages Intercept Interviews High data quality High cost High response rate Allows for complex surveys Mail-back and Hand-back Intercept, Lower cost than intercept Lower response and data quality and Mail Useful for short and simple than intercept surveys Slow for mail and mail-back surveys Internet Low cost Low response rate Automated data processing Requires access to the Internet Limited complexity Telephone Allows representative sample of Moderately high cost and time to large and dispersed populations implement survey such as business firms 2.3 Survey Frequency and Timing 2.3.1 Dealing with Seasonality Several aspects related to timing and frequency need to be considered in planning an airport user survey project. The pattern of air travel at most airports varies seasonally. Performing a pas- senger survey at only one time of the year will not reflect the variation in traveler characteristics and thus may give a biased picture of the composition of the air travel market over the year. On the other hand, if data on air traveler characteristics are needed for planning airport facilities for their peak use, then the survey should be performed during the peak demand period. While it is common practice to design airport terminal facilities for the average day of the peak month, some thought should be given to likely conditions during other peak periods, and it may be desir- able to collect passenger survey data at those times as well. The highest hourly demand on air- port facilities may not in fact occur during the busiest month, but rather may take place around holiday weekends at other times of the year, such as Thanksgiving. Seasonal changes in the composition of the air travel market can have a particular influence on airport ground transportation mode use. Figure 2-1 shows the monthly variation in use of short- term and long-term parking at Los Angeles International Airport over a two-year period in the early 1990s, expressed as parking exits per hundred passengers (Gosling, 1996). Use of short-term park- ing varies inversely with use of long-term parking: Short-term parking use is highest in the summer and in December and January, both times associated with higher levels of non-business travel. Long- term parking use is highest in the spring and fall, months with generally higher levels of business travel. Similar seasonal patterns have been observed at other airports and for other ground access modes. It is clear from Figure 2-1 that depending on the month in which an air passenger survey is performed, the use of airport parking indicated by the survey results would differ considerably. It should be noted that the monthly volume of passenger traffic through the airport and the com- position of the traffic are really two different issues, as illustrated in Figure 2-1, which has been adjusted for the variation in air passenger traffic. One approach to accounting for seasonal varia- tion in calculating the market composition for the year as a whole is to use a weighted average of results obtained during two survey periods, in a peak traffic month and an off-peak traffic month. While the market composition during the peak traffic month is usually different from that during the off-peak months, in fact the composition is likely to vary throughout the year. The market com- position for the year as a whole will generally be different from that given by the weighted average of results obtained during a peak traffic month and any one off-peak traffic month.

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Planning a Survey 17 14 Parking Exits per Hundred Passengers 12 10 Short-Term Parking (up to 6 hrs) 1993 Long Term 8 1994 Long Term 6 1993 Short Term 1994 Short Term 4 Long-Term Parking (over 6 hrs) 2 0 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Source: Adapted from Gosling, 1996. Figure 2-1. Variation in parking use--Los Angeles International Airport. A number of methods can be used to deal with seasonality: If the attributes being measured are for use in assessing facility requirements and capacity constraints, values of these attributes during the peak planning period may be of interest; if so, conduct the survey during this period. Conduct the survey in a shoulder month that is considered to be the most representative of average traffic over the year. Conduct the survey in several waves, such as each quarter, each month, or during peak and off-peak months. Use continuous or rolling surveys conducted throughout the year to allow the seasonal vari- ation to be measured directly. The use of continuous or rolling surveys has a number of advantages besides providing good information on seasonal variation of market composition. These advantages include the need for far fewer survey personnel, who in consequence can be better trained and will become more expe- rienced, improving the quality of the survey results. This approach also makes the survey results far less vulnerable to distortion from atypical events that happen to occur during a survey con- ducted over a much shorter period, such as unusually bad (or good) weather, major sporting events, or labor unrest. A survey performed on an ongoing basis from year to year will also provide some early indication of trends in market composition that might be missed (or misinterpreted) if surveys are conducted only periodically. The continuous survey approach has been adopted by the United Kingdom Civil Aviation Authority (UK CAA) for its program of air passenger surveys undertaken at the 14 largest U.K. airports (UK CAA, 2006). The survey teams spend several days at each airport before moving on to another airport, returning to each airport every few weeks. 2.3.2 Multi-Year Considerations In addition to accounting for seasonal changes, a related consideration is how often airport user surveys need to be performed to identify changes in market composition that are occurring