Would these work mounted in a van? Do they latch securely enough that they would not slide open in transit?

Festool's manual for the SYS-AZ drawers advises against using them for use in vehicles. However, you can find examples online where people have used them in work vehicles. Here's one example:http://festoolownersgroup.com/workshops-and-mobile-vehicle-based-shops/sys-az-drawers-in-sprinter