Sample validity

The present study attracted a much higher number of IVNS users than the previous study.

Drivers of all ages were well represented. In light of the previous sample and due to previously highlighted difficulties in attracting elderly respondents in IVNS user research (Green, 2001), it was particularly surprising that older (>=60) and younger drivers (<=29) were so well represented. Figures 4.3 and 4.4 can only be used as a rough guide to establish sample representativeness as they relate to UK drivers only and the present sample was more culturally diverse, but they do illustrate quite well that in terms of age, a fairly representative sample of drivers participated.

Similarly there were wide ranges in terms of the number of years holding a driving license, mileage and IVNS experience. It is likely that these sample characteristics could at least partially be attributed to the much wider sampling frame used in the present study. As some authors (e.g. Joiner et al, 2005) have expressed concerns about gender disparity on specialist websites and because it was likely that the previous study also attracted a high proportion of

24%

38%

3%

8%

12%

1%5%

9%

Too expensive/ awaiting offer System too new

Didn’t know they needed updating Don’t use system often enough Don’t need to (yet)

Don’t know how to/ don’t know how often updates released Not available

Other (inc. forget, loss of software features, area not covered)

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driving and IVNS-related internet forums, bulletin boards and mailing lists, the survey was also advertised on other general interest internet forums as well as those specialising in issues unrelated to driving and IVNS.

It was hoped that adopting a much wider sampling frame would also attract a much higher proportion of female IVNS users, but the results clearly show that still only a small minority participated (although they were represented in almost every age band). As noted in the previous chapter, other online IVNS user studies have had similar difficulties attracting female participants (e.g. Varden, 2008; Li, 2006). Varden (2008) suggested this could simply mean that a much higher proportion of males use IVNS than females. The previous study partially supports this assertion as it attracted a high proportion of female drivers, but only a very small proportion of female IVNS users. In a review of several online studies, Krantz and Dalal (2000) noted a wide range in the dispersion of females across studies ranging from 7%

to 71%. Hewson (2003) suggests that the gender of the sample will depend very much on the topic being investigated. For example Gosling et al. (2004) cited a questionnaire study that sampled pet owners, in which 83% of participants were female. In the last few years several authors have concluded that men and women use the internet in equal numbers (e.g. Lenhart et al, 2003; Gosling et al., 2004).

While some other IVNS user surveys employing more traditional methodologies have attracted higher proportions of female respondents, in most cases they have included much higher proportions of males (e.g. Svahn, 2004; J.D. Power, 2004-2008). The DfT (2005) survey reported that an equal proportion of males and females had an IVNS in their car, but the question was worded so that it is not clear whether respondents merely had a system in their car, used the system or owned it. In the US, the national highway traffic safety administration (Royal, 2003) surveyed over 4000 drivers, and found that only a slightly higher proportion of males (6%) reported owning an IVNS than females (5%), although a higher proportion of males (10%) than females (7%) reported owning PDA`s. In a recent survey, most female drivers (60%) also indicated that they would feel safer with an IVNS, suggesting there is demand from female consumers. (Zoomerang, 2006). It is unlikely the findings reported in the present study and other online studies reflect the true proportions of female IVNS users in the driving population, and this limits its’ external validity. Gender disparity in IVNS use will probably both reduce and become much clearer over time as the price of IVNS continues to fall, the range of devices capable of performing route guidance

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from the present study and from previous studies that sampling frames must be carefully designed and appropriately wide to attract female IVNS users whether the studies employ the internet or more traditional methodologies.

The present study attracted a culturally diverse sample drawn from North America, UK and the rest of Europe. This was important as it provided insight into behavioural adaptation issues affecting all drivers, regardless of individual country idiosyncrasies. A drawback of other IVNS user surveys (e.g. Svahn, 2004 sampled German IVNS users only; DfT, 2006 sampled UK drivers only) is that they employed culturally specific sampling frames. Another drawback of some previous surveys is that they only sampled integrated IVNS users (e.g.

Svahn, 2004; J.D. Power, 2003-2008). The present study sampled a much wider range of IVNS users; including those using PDA/mobile phone based systems, nomadic systems, integrated systems as well as home-made systems. Chapter 2 noted system variation as a key problem in interpreting many of the results from experimental studies that had compared driving behaviour using paper maps with IVNS. While this is a major drawback when comparing controlled experimental studies with specific hypotheses, it can be useful in initial surveys such as the present study, as it allows researchers to find out about some of the wider issues regarding behavioural adaptation to IVNS affecting most IVNS users, regardless of individual system idiosyncrasies.

Students and unemployed drivers were under-represented in the present sample, but it did attract a wide range of drivers who were self-employed, employed and employed in managerial positions. Although the market penetration of IVNS continues to increase and their cost continues to fall, recent surveys have suggested that the majority of IVNS users are employed at some level (Svahn, 2004; DfT, 2006). Drivers unskilled in computing were also severely under-represented in the sample, and it is likely that this was directly due to the sampling frame.

Overall, with the exception of a few discrepancies (e.g. gender) the sample was fairly representative in terms of most demographic factors. This helps to strengthen external validity. Table 4.3 shows that in most cases, the sample is broadly similar to that obtained in another user survey using traditional methods. In fact, table 4.3 suggests the present study may be even more representative in terms of socio-economic status, presumably because it

150 acceptance of IVNS