Why would less cars mean more shipping trucks? I don’t understand what you’re trying to say here.
Companies which rely on transporting products between different locations (like Amazon, UPS etc) will make use of emptier roads to transport more goods. More empty roads = more opportunities for operational efficiency for transportation companies
Edit which isn’t a bad thing per se, companies should get to be more efficient, but not at the expense of tax payers who don’t want to subject themselves to public transport