Research Postar model Seasonal and daylight variation

The hours of daylight vary with the seasons. Unless a site is illuminated, the propensity for it to be seen will change throughout the year as more and then less daylight is available. Any billboard campaign is subject to seasonality.  Postar is corrected to account for daylight hours. 

Opportunity to see (OTS) is calculated by the application of the percentage traffic by hour to the full day profile.  As a result, a campaign of non-illuminated sites running in January will receive only half of the OTS it would obtain in the summer months. 

To reflect the varying spread of daylight in Great Britain, the country is divided into three, with London, Liverpool and Glasgow as the epicentre of each area.  Sunset and sunrise times are taken for the 15th of each month.  The traffic profile for that day is obtained from the Department for Transport and the proportion of the daily traffic is calculated for each hour of the day.  To calculate the total proportion of daylight traffic for each month of the year, the lighting up time is then taken into consideration.  Half an hour is added to the sunrise time and half an hour subtracted from the sunset time.  The proportion of traffic in the reduced sunset and sunset hours is added to the proportion of traffic in the intervening hours of full daylight.  This gives a total proportion of daylight traffic for each month of the year.

These calculations affect OTS by highlighting the difference between illuminated and non-illuminated campaigns. These differences will be magnified during the winter months.  There will be significant drops in reach and frequency if the campaign is non-illuminated. 

Postar therefore produces seasonally adjusted cover and frequency estimates.