Pivot table - SUM of COUNTS?

Here's the premise:

Vehicle crashes have stored with them many fields of data. Each row of my table contains (for example) location, crash type, speed, year occurred, vehicle type and details on up to four drivers/pedestrians involved (by a set of columns that repeat four times). Each driver's age is recorded in a column called AGE with values ranging from 0 to 900 or left blank depending on how many drivers were involced.

Here's a rudimentary example of what it looks like using commas as column breaks (you'll have to use your imagination):

YR,AGE,AGE,AGE,AGE
2005,18,22
2001,16,64,28,27
2008,78
1997,35,12

So I have four AGE columns displaying ages of drivers. In a pivot table, I want to SUM the COUNTS of each age within all of the four columns by the year the crash occurred. So the table has to be smart enough to know that for every crash that occurred in 2005, XX drivers (of up to four possible drivers) were XX years old.

As it stands so far, I can get a pivot table (and subsequent graph) to show me a multi-year breakdown per driver column by age (AGE, AGE2, AGE3, AGE4) or even by age groups that I determine (AGE5), but I can't get it to combine the counts from each AGE column into a singular column representing that particular age.

The icing on the cake would be to be able to define my own age groups as well using preset criteria (less than, greater than, etc.) because the age data can be so variable.

I hope I supplied enough info.