"ET", meaning Expedited Transportation, I presume?
Diane and I ran almost three years without a portable toilet in the fleet-owner trucks we then drove. While we know many drivers who carry portable toilets or other solutions to nature's call in their trucks, we never did. That meant we always used public bathrooms and sometimes had to drive for a half hour or more to find one at odd hours. Yes, you can get along without a toilet in the truck, but it is not always easy.
That was then. Now, as I write this, we're sitting not in a truck of our very own. It has an RV-style toilet and shower in the sleeper. At 9:30 PM on Sunday, we're backed up to the consignee's loading dock. No one is around. The neighborhood is safe. The business is closed until tomorrow. Delivery is scheduled for 8:00 AM.
Because we have a toilet in the truck, we can park at the delivery. We won't have to use fuel driving around looking for a place to park that has a toilet. We won't have to get up an hour earlier in the morning to drive from our overnight parking spot to the consignee. We'll crank the engine over one less time since when we start it up in the morning it will be to pull away from the dock we're now at.
Tonight, we'll get a full night's sleep, knowing that when nature calls, we won't have to go searching for a toilet or walking across a dark parking lot someplace else to use one.
Having a toilet of some sort in the truck is safer, more convienent than not having one. It will give you more time to sleep, reduce your fuel consumption and reduce wear and tear on your truck.