The 407 people go by the registered weight of your vehicle. I used it with just my TV which in season is registered at 11,000 kilos or 24,600 lbs. They wanted over $300. dollars from me for a round trip from the 400 to the 401. I called them and they reduced the charge to around $60. So if you take the 401 to the 400 north you won't have to worry about a transponder or having to pay whatever the 407 people will charge you. It's not that far out of your way. If you take the 402 from Sarnia you will still have to get on the 401 to Toronto to the 400, unless you travel the routes mentioned above.