hi all,
after my first week as a new driver and new job, I got myself a garmin nuvi 50, is there a sd card update I can buy for trucks, got myself into a bit of a tizz yesterday but all ended ok…cheers.
I’m not familiar with Garmin sat-navs but you would almost certainly get an answer to your question at www.navitotal.com
Yes, tachograph is spot on. Exactly what I was going to suggest! 
That website is your best bet. If there isn’t a truck specific map for that satnav, then you may find somebody has edited the normal car one to warn of low bridges, height and weight restrictions etc.
Good luck!