Title: The M74 study: longitudinal follow-up of the health effects of a new urban motorway
Funder: Department of Health (England)

Abstract: DESIGN. Mixed-method study using a combination of quantitative and qualitative research methods to evaluate both individual- and population-level changes in health and health-related behaviour coupled with achieving an in-depth understanding of how these changes are experienced and brought about. The study will comprise three main components: (1) CORE SURVEYS OF LOCAL STUDY AREAS to compare changes in neighbourhood perceptions travel behaviour physical activity and wellbeing in the intervention and control areas by means of combined cohort (baseline achieved total n=1322) and repeat cross-sectional (target total n=3000. minimum required total n=1200) follow-up surveys of local residents coupled with an environmental audit (documentary analysis interviews and site visits) to ascertain whether the intervention was implemented as originally planned to elucidate its broader environmental impact and to identify any potential area-level confounders. (2) TWO-TIER IN-DEPTH STUDY of a subsample of core survey participants to quantify differences in neighbourhood-specific physical activity between intervention and control areas (combined accelerometry and GPS measurement target n=400: 200 intervention + 2x100 control) and to elucidate participants’ experiences of environmental changes and the mechanisms through which these changes influence behaviour (qualitative interviews target n=60: 30 intervention + 2x15 control). (3) ANALYSIS OF EXISTING NATIONAL POPULATION DATASETS to evaluate the impact of the intervention on road traffic casualties and to describe concurrent regional and national trends in travel behaviour and neighbourhood perceptions.SETTING. Matched intervention (n=1) and control (n=2) deprived urban areas in Glasgow (see sections C2 and C3). TARGET POPULATION. Householders living in areas previously surveyed in 2005 (see sections C3 and C5). Baseline respondents included both more and less affluent groups (e.g. 52% owner-occupiers). INTERVENTION. The new urban section of the M74 motorway and associated changes to the local urban landscape (see section C2 and m74completion.com).OUTCOMES. Changes in three measures of travel behaviour over an eight-year interval from baseline (2005) to follow up (2013): walking for transport (min/day) cycling for transport (min/day) and car use (min/day). Differences between study areas in time spent in moderate-to-vigorous physical activity within the neighbourhood (nMVPA: min/day). Changes in the monthly incidence of killed and seriously injured (KSI) road traffic casualties between 1995 and 2013 and in their distribution by type of road user class of road and small-area socioeconomic status of location of incidents. Changes in neighbourhood perceptions and SF-8 physical and mental summary scores. Differences between study areas in time spent in overall MVPA (min/day). An understanding of what environmental changes have occurred in practice and how their effects have been mediated and experienced.KEY SAMPLE SIZES. For TRAVEL BEHAVIOUR a cross-sectional sample of 400 per wave per study area (exceeded at baseline) would be expected to allow the detection with 95% confidence and 80% power of an increase of 5 min/day in walking for transport from baseline to follow-up within one study area or a cross-sectional difference of 2 min/day in cycling for transport or 5 min/day in walking for transport between intervention and control areas at follow-up. The availability of two control areas a larger follow-up sample than the minimum of 400 per study area and the potential to compare longitudinal changes between study areas using a combination of cohort and repeat cross-sectional analyses will increase the power of the study to detect smaller changes. For objective PHYSICAL ACTIVITY measurement 86 participants per group would be required to detect a difference of 3 min/day in nMVPA between intervention and control areas. Our target total achieved sample of 400 participants in objective monitoring would be more than sufficient to achieve this. For INJURIES a minimum of 50 time points is recommended for interrupted time-series analysis of the type we intend to use. The STATS19 dataset from 1997 to 2013 contains 204 monthly data points and therefore easily exceeds this minimum recommendation.ANALYSES. Multivariable regression analyses of the effect of exposure to environmental changes on travel behaviour and neighbourhood perceptions; the sociodemographic distribution of those changes; and their relationship with changes in overall physical activity and wellbeing. Merging of accelerometer and GPS data followed by buffering of the combined dataset in a geographic information system (GIS) to identify nMVPA followed by adjusted multivariable regression analyses of differences in nMVPA between study areas. Mixed-method thematic analysis of qualitative data linked to spatially-referenced activity data. Autoregressive integrated moving average (ARIMA) interrupted time-series analyses of changes in injury rates; multivariable regression analyses to explore changes in sociospatial distribution of injury incidents. Repeat cross-sectional analyses of Scottish Household Survey data. TIMETABLE. Jan-Aug 2013: Refine study design and survey instruments; apply for ethical approval; commence documentary stage of environmental audit; prepare for survey data collection. Sep-Dec 2013: Collect survey data (completed in two months at baseline); complete documentary stage of environmental audit. Jan-Mar 2014: Clean survey data; prepare for objective measurement and qualitative fieldwork. Apr-Dec 2014: Analyse survey data; collect objective measurement data (with an issued sample of 30/wk as previously achieved in our PHR-funded study 09/3001/06); undertake qualitative environmental audit and interview fieldwork. Jan-Dec 2015: Complete all remaining analyses and write up.


Research activity codes: 3.2 INTERVENTIONS TO ALTER PHYSICAL AND BIOLOGICAL ENVIRONMENTAL RISKS
Health categories: GENERIC HEALTH RELEVANCE