In terms of emissions, you wont come close to what a diesel long haul truck is putting out, and those are the vehicles no one really talks about. Freightliner and peterbilt all showcase their latest trucks with urea scrubbers and nox emissions reduction technology, or even hybrid/electric systems when they go to trade shows, but most fleet operators are on a 30 year curve. No trucking company wants to buy a truck new.
and thanks to loopholes in EPA regulations they dont need to. fleet owners can do whats called a "glider" conversion. You essentially take the guts of a 30 year old tractor trailer, and wrap it in a nice new body. this works well to refurbish trucks that have been in rollover accidents or written off by insurance companies. they are easier to move from salvage to titled.
Assembly of a glider is also prone to problems. Professional mechanics can do it well, but its not cheap, so to drop the cost of a glider most fleet owners sub this work out from their main shops to subcontractors of Salvadorian day laborers. The result is that the truck runs, but critical things like the urea tank wont run, the pyrometer is broken, and the dashboard lights up like a christmas tree. Ive even seen gliders where the speedometer was so incorrect, the driver told me to "use the gps" on my phone instead.
These trucks are miles off spec for EPA, but most states only halfheartedly enforce the EPA regulations for trucks. Fleet owners title them in states like Indiana, florida and Ohio for a reason: these states couldnt care less if the truck smokes out the parking lot of a wal-mart just starting up.