The purpose of this study is to examine the spatial and temporal characteristics of weekend work episodes. Specifically, we examine whether individuals work over the weekend and, if they work, whether they work at home or outside the home. We also model the time of day of weekend work. The empirical analysis in the paper is based on the 2000 San Francisco Bay Area Travel Survey. The results indicate the important effects of day of week/seasonal effects, individual demographics, work-related variables, household characteristics, and location variables on weekend work participation characteristics. The models estimated in the paper may be embedded within a larger weekend activity-travel pattern forecasting model system. Sall and Bhat 1 Travel demand modeling has traditionally focused on understanding and modeling individual activity-travel patterns during the 5-day work week (Monday-Friday). This focus on the weekday stems from the intense traffic congestion prevalent in most urban areas during the morning and evening commute periods. In contrast to the substantial attention on weekday activity travel patterns, little or no attention is accorded to weekend activity-travel pattern analysis within the context of travel demand modeling. However, in recent years, the overall magnitude of travel and the intensity of traffic congestion during weekend days have increased to the point where these levels are approaching weekday levels. In the rest of this introduction section, we motivate the importance of examining weekend activity-travel patterns in general (Section 1.1), briefly review earlier studies examining weekend work participation (Section 1.2), and present the specific objective of the current research (Section 1.3). There are three reasons why an examination of weekend activity-travel patterns is important A second reason for examining weekend activity-travel patterns is that the temporal and spatial characteristics of weekday and weekend day trips are quite different. For instance, weekend travel does not follow the same peaking characteristics as weekday travel. Lockwood et al. indicate that the weekend travel peak period is during the midday, and find that the length of this peak period is larger than the morning or evening peak periods during the conventional work week. In addition, there could be unique traffic generators (such as sporting events or cultural events) during weekends, resulting in traffic characteristics that are very different from that of the typical weekday. The net result is that the network links that are congested during the weekend days could be very different from those that are congested during the weekdays, and the peak periods generally occur at times that are different from the traditional weekday peak periods. A third reason for studying weekend activity-travel patterns is that weekend trips have a significant effect on air quality. The peak period for weekend travel occurs during the midday, when temperatures are higher (Lockwood et al., 2005) . Since higher temperatures facilitate the formation of ground level ozone, the result is potentially higher ozone formation per vehicle mile traveled on weekend days compared to weekdays. In fact, air quality investigations by Marr (2002) show that ground level ozone levels, and associated health problems, have been more prevalent during the weekends compared to weekdays for the past 20 years in California. Sall and Bhat 3 The once-dominant traditional Monday-through-Friday, nine-to-five, workweek has given way today to more flexible work arrangements, thanks to the demand for 24-7 services, and the advent of internet and computing technology. Interestingly, there have been several studies in the sociological literature focusing on the benefits and costs of weekend work and in-home work. Tausig and Fenwick (2001) found that the benefits of an alternate work schedule on balancing family and work lives are only likely to be realized when the schedule is voluntary. They also point out that working over the weekend displaces family time, thus potentially increasing work-family conflict. Similarly, while increased family time and reduced childcare costs are often identified as benefits of in-home work, such an arrangement does not necessarily benefit the family or finances. From a family standpoint, research has consistently indicated that the key to successful home-based telework is the maintenance of a firm separation rather than integration of work and family activities (Mirchandani, 2000; Fitzgerald and Winter, 2001 ). There are three reasons for the importance of this separation: role meshing reduction (see Pleck and Staines, 1985; Kingston and Nock, 1985; Kinnunen and Mauno, 1998; White and Keith, 1990) , less workaholism, and the protection of Sall and Bhat 4 professionalism (Mirchandani, 2000) . In the context of workaholism, Mirchandani observed that the flexibility gained by working at home is "paid" for by working on average 2.5 hours/day more. From a financial standpoint, working from home may entail childcare payment to achieve an undisturbed work environment. While the above discussion indicates that there has been earlier sociological research studying the benefits and costs of weekend work (and in-home work arrangements as part of weekend work), we are not aware of any earlier research in the transportation literature that examines the propensity to undertake weekend work activity and the spatial/temporal characteristics of such weekend work activity. As discussed in detail in Sall (2004) , weekend work activity decisions can be used to generate overall weekend activity-travel patterns. The purpose of this study is to examine whether an individual works over the weekend and, if s/he works, whether the individual works at home or outside the home (i.e., the presence and location of work). We also model the time of day of weekend work (i.e., the temporal dimension of any work activity). Our analysis is motivated by the fact that, while there has been extensive study into weekday work-related attributes and weekday activity-travel patterns (see Damm, 1980; Bhat and Singh, 2000; Pendyala et al., 2002; Strathman et al., 1994) , there has been little to no examination of weekend work-related attributes and weekend day activity-travel patterns. The rest of the paper is structured as follows. The next section discusses the methodology and model formulation for our study of weekend work participation. Section 3 identifies the data source and sample used for the analysis. Section 4 presents the empirical results. Section 5 summarizes our findings and implications. Sall and Bhat
Sall et al. REF studied weekend work activity patterns in the San Francisco Bay Area using surveys.
An Analysis of Weekend Work Activity Patterns in the San Francisco Bay Area
Transportation
Economics