Hi Gary ( @gmanuki ),
this is an excellent question - never thought about that problem.
I would create another liquidtemplate, which retrieves the vehicle from the table for which the id is passed in. May be see https://docs.microsoft.com/en-us/power-apps/maker/portals/liquid/liquid-objects#entities for details on the entities tag. could be something like
{% assign myvehicle = entities.my_linking_table[request.params['id']].myvehiclelookup.id %}
Then you have in myvehicle the id. You could either open a form on that page with that id or reroute to a page with lets say:
<script>
var myvehicleid = "{{ myvehicle }}";
window.location.href = "/myvehicleeditpage/?id=" + myvehicleid ;
</script>
Hope this points in a solutiondirection for you.
Greetings from northern germany,
Christian