You can have this employee follow the trainig as a transport escort at a training institute in the Netherlands. This employee must pass both the theoretical and practial exam. Subsequently, an Aanstellingspas for a transport escort can be requested.
You also have the option to go through an adaption period based on the regulations. You can find this in the Regeling Verkeersregelaars.
Additional regulations on this subject can be found at de website van de Rijksoverheid.