After seeing examples of this, I've never been happy with ACW62 - Wagons.

Look at the photograph.
https://pendraken.co.uk/19th-century/americas/american-civil-war/
There is no foot rest for the driver. His legs are dangling. In real life, when that wagon stops, he's going to slide forward or do a Charlton Heston (Ben Hur) impression, landing between the two rear horses!     

So, after some research, I've finally discovered that it appears we've all been watching too many cowboy movies and that most ACW supply wagon drivers sat on one of the rear animals and drove the wagon from there in a similar way to artillery limber outriders.   

Of a number sources consulted, this is one of the most informative about Civil War Era road transportation:-
http://projects.leadr.msu.edu/civilwarera/exhibits/show/acw-logistics-transportation/acw-lt-roadtranspo-wagon-mule

In this, it confirms that "Wagons were controlled by a driver, who actually sat on the left rear mule/horse, not on the wagon itself (a common misconception about the army wagon). The driver would control the four-six mule teams with a variety of reins, a whip and occasionally a braking apparatus."

The article also includes a good photograph in which (when you enlarge it) you can actually see the drivers sitting on the mules.

http://projects.leadr.msu.edu/civilwarera/files/original/6c876e90cb3c2e622921269d45ad7bf0.jpg

There is also another one of wagons entering Petersburg when you click on Use of Wagons: USA v CSA.

http://projects.leadr.msu.edu/civilwarera/exhibits/show/acw-logistics-transportation/item/167

For those so inclined to remedy this anomaly, what is the solution? Well, apart from scratch building a foot board for the poor guy, perhaps Leon will provide additional horses with outriders on request. Or, failing this, simply 'pinch' these from ACW66 - Caisson with limber & team?  Wagons ho! 

That's a good point on the kickboard, I'd not really noticed that before!  Our Boer wagons have got kickboards on them interestingly. 

The easy option from our side is to supply the limber/caisson ridden horses for anyone who wants them, no worries.

Superb response.

Now that Westmarcher mentions it, I recall hearing about the ridden horse on American wagons.
The context was an analysis of why nations drive on the left or right.

Larger American and Continental goods wagons had a driver riding a draft animal (Larger teams, driver nearer the front) which eventually led to passing on the driver's side / driving on the right.

The theory about Britain's was somewhat older, connected with mounting horses from the left to keep the sword free.
Also something that sounded quite apocryphal: Preventing bandits gaining advantage from a shield.