Shopping aisles

Yours truly spends part of each week in Exeter's city centre shops, as part of my responsibility as a chaplain to some of the shops.  One of these has just been revamped and I realised that part of the rearrangement of the store had led to a change in the width of the shopping aisles. 

The main floor is arranged around one long central aisle, with shelves and racks to each side.   The aisle is marked with a hard-wearing surface, more durable than the surface around the sales area. Customers use the aisle to move around the different sections of the store, before browsing on those shelves and racks.  So it has to be wide enough for people to pass as they walk.  But shoppers come in families, and so they don't walk in single file.  They come with buggies, prams, wheelchairs.  So, this main aisle has to be wide enough to be comfortable for such shoppers, but not too wide that sales area is lost. 

The width is a number, so there is some maths in it.  How is it determined?  Trial and error?  Someone has made a decision, a possible application area for O.R., and - in Exeter - it looks to be the right one.  Customers flow well, even at busy times.