This study identified that individual factors and aspects of the social and physical neighbourhood environment were associated with children's participation in active free-play in particular outdoor locations. The yard at home was the location where parents reported that their child played most often on both weekdays and weekend days, therefore, it seems plausible that finding ways to optimise children's active free-play in this setting may be an important aim of future research.
Consistent with previous studies that have shown individual physical activity preferences to be associated with children's overall physical activity [8, 17], this study showed that parents who reported that their child preferred to spend time engaged in activities that did not involve physical activity were also less likely to report that their child play in the yard at home on the weekend. This variable relating to child's preferences was the only individual variable that was associated in the multivariable analysis with playing in any location and was only associated with playing in the yard at home and not in the child's street or local park. Although research among both adults  and youth  suggests that physical activity and sedentary behaviours can co-exist with each other, identifying and promoting physical activities that children enjoy and prefer to do may increase frequency of playing outdoors.
A number of social environmental factors were found to be associated with children's active free-play. A plausible explanation for the finding that children whose parents perceive a high crime rate play more in the yard, may be that these parents consider the yard a relatively safe environment and encourage play in the yard at home instead of other outdoor locations such as play in the street or park. This could be considered encouraging as at least the children are still playing outdoors, and is consistent with other cross-sectional studies that have suggested that parents' perceptions of neighbourhood crime may influence children's outdoor play .
The importance of social networks and friends to activities performed outside school hours has been identified previously [7, 21, 22]. This study found that parents who reported that their child had many friends in their neighbourhood were more also likely to report that their child played more regularly in their own street/court/footpath. This suggests that in order to increase children's active free-play it may be important to develop and foster social networks within the neighbourhood so that families and children can establish links for active free-play. This may involve developing community family days or other social events where families have opportunities to interact.
Previous cross-sectional studies have reported mixed results about correlations between neighbourhood safety and children's physical activity [23, 24]. In the current study, parents' perceptions that it was safe for their child to play in the street outside their house was positively associated with parents' reporting that their child played in their own street/court/footpath more regularly on both weekdays and weekend days. This study did not measure real safety and therefore it is not possible to determine if there are gaps between real and perceived safety issues. Increasing real safety within the neighbourhood is likely to have positive implications for children's active free-play. In order to maximise opportunities for children to play in their street and other outdoor places, it may be important to develop education campaigns for parents about real versus perceived risks relating to children's active free-play and provide children with additional knowledge and skills for playing safely in their neighbourhood.
Whilst previous review papers have shown conflicting results for studies assessing street connectivity and physical activity among children , the findings from the present study indicate that living in a court/cul-de-sac was positively associated with play in the child's street. Literature regarding adult physical activity suggests that connecting streets and through-roads are important for promoting walking among adults ; however, in this study connecting or through-roads were inversely bivariably associated with the child playing in their own street/court/footpath. It is also possible that connecting streets may be important for children's active transport, but not so conducive to active free-play. It may be necessary to design street networks that provide the safety of a cul-de-sac to promote children's active free-play whilst also allowing connectivity to encourage walking among adults. Other alternatives may include providing connections between streets that are accessible by foot rather than vehicles and limiting through traffic in specified neighbourhood streets during after-school hours.
Parents who reported visiting parks as a family were more likely to report that their child played in the park/playground on a regular basis. Park use by families may be increased if parks are easily accessible, located close to home and provide facilities that are appealing to children of all ages [7, 8]. Further studies that investigate issues surrounding playground facilities and involve children in the design process may encourage use of local parks by children and families. It is also possible that parental safety concerns about park use may be reduced if children visit parks that are located close to home [7, 8].
This study showed that the frequency with which children played in the specified outdoor locations was not associated with overall objectively-assessed physical activity levels. This lack of association may be due to the non-specificity of the objective physical activity measure. That is, children may have high levels of physical activity because they were participating in other forms of physical activity such as organised sport. It is also possible that all children did not have equal amounts of free-time in the after-school period to engage in physical activity and this could potentially have an impact on the results. Finally, it is important to recognise that only the frequency of playing in particular outdoor locations was measured and future studies of active-play that measure time spent playing in each location may show associations with overall physical activity levels. Further investigation is warranted as it is probable that active free-play has the potential to make an important contribution to children's overall physical activity; however, no other Australian studies have assessed physical activity specifically in this domain.
The consideration of influences at the individual, social environmental and physical environmental level was a strength of the study design; as was the test re-test reliability of the outcome and predictor variables and the objective measure of total physical activity. Limitations include the use of a parent-report survey which relied on parents answering the survey honestly and accurately and the cross-sectional design which prevents inferences about causality. Although power calculations suggest the study was adequately powered to detect significant associations, there were smaller numbers of participants in certain categories which may have resulted in insufficient power to detect some associations between variables.