Multi-level aggregation using DAX measures

You may want to look at Date-Time Table with granularity for every hour of the day for every day from 2012-2018 then relate that to yoru Date and Time by hour column. You then just need to write a Simple Measures for the averages. Total Average = AVERAGE(table[total vehicle counts])

You can then use the Time Inteligence features of DAX.  Tip youse the Day, Hour, Week, Month, Year from the date-time table not your Data Table and to keep things clean I'd remove all your Date and time related columns other than your Date/Time column.

See this link for creating the DateTime Table in Powerquery https://community.powerbi.com/t5/Desktop/Has-anyone-created-datetime-table-using-QueryEditor-or-DAX/m-p/317403