Summerhouse Travel Activities in Attica: a Panel-based Comparative Approach
A Deloukas, Attiko Metro, GR
Discrete panel data are used to model the seasonal mobility within Attica during the summer holiday period.
A large household travel survey, conducted during two consecutive seasons in Attica for the needs of the Metro Development Study (MDS), confronted complex design and execution issues. The paper discusses the variation of household and travel characteristics drawn from a panel containing same households and the same type of information across periods. Discrete panel data are used to model the seasonal mobility within Attica during the summer holiday period.
The study area covers 79 municipalities in the Greater Athens Area (GAA: 94% of Attica population) and 38 in the Rest of Attica Region (RAR: 6% of the said population). Section 2 of the paper discusses the design of the panel survey. Wave 1 covered the typical (spring) and wave 2 the summer period (July-August). In wave 2, a subsample of wave 1 households (hh) has been re-interviewed. The same questionnaire (with small modifications for the household and person data parts) has been used over both periods. The trip diary recorded weekday trips only. In such a controlled experiment design, person-specific characteristics remain essentially the same, and the temporal variation refers to certain household and travel characteristics. The sampling rate amount to 2% of the Attica population in the typical period (27?696 hh), large enough to get reliable population estimates. In the summer wave the rate was 0,5% in the GAA (i.e. every 4th of the hh sampled in wave 1) and 2% in the RAR. Publicity actions have given rise to a higher response rate in both periods and a lower attrition rate of the summer wave. Regarding the hh that participated in wave 1, the response rate in wave 2 amounts to 68% (rest: dropouts 12%, non-contacts 20%). Ultimately 74% of the total summer sample (8?002 hh) had participated in both waves. The attributes of people who refused to report again in wave 2 have been analyzed and compared with acceptors based on their characteristics drawn from wave 1 (self-selectivity and attrition effect).
In section 3, the seasonal variation of certain household and travel characteristics is examined at an aggregate level. The summer population reduces in GAA by 16% and increases in RAR by 58%. Most of the households residing in the GAA retain the same residence over both periods. In the hot summer period though, numerous households migrate as a whole or as a part to a summerhouse in the RAR. Indeed, almost 150?000 persons are seasonally living during the weekdays at a summer house in RAR. The wave 2 hh size reduces by 3,4% in GAA and increases by 4% in RAR. From wave 1 information comes out that almost 10% of the hh population owns a summerhouse in RAR. However, linking information of both waves, only 1/3 of such residences are occupied during the summer weekdays. Referring to travel characteristics, the summer trip rate in GAA remains virtually stable, while in RAR increases by 5% as compared to the typical period figures respectively. Due to the extended trip length, the seasonal mobility level increases as a whole. The abovementioned figures have supported the planning of the 2004 summer Olympics, especially exploiting wave 2 information.
Section 4 targets the population living in GAA and owning a second home in RAR. The discretionary decision to effectuate a relocation of the residence during summer weekdays is modeled with logit structures. Socioeconomic variables tested include i.a. the level of car availability exerting a positive influence, the number of breadwinners and their current employment status having a negative impact, as well as life-cycle attributes such as the number of pre-school children affecting the decision in a positive way. Trip-related variables exerting a negative influence refer to the differential commuting travel time of working hh members. Logit models calibrated with wave 1 information, as well as with choice-based wave 2 information are compared. The former models are validated using the revealed preferences drawn from the wave 2 information.
The findings concerning the summer migration within Attica are of particular importance for rapid growth areas in the Rest of Attica Region as demonstrated in the MDS projections. Planned highway and rail connectors to Messogia (Rafina, Lavrio) in the East and Salamis in the West will certainly intensify the summer season mobility in this respect.
Association for European Transport