Dispatching
Pick up a load with an appointment time of 8:00am and deliver it 650 miles away by 8:00am the next day. Sounds reasonable.
The rules of the road - (just the very basics)
You can drive 11 hours within a 14 hour period. You then must get 10 continuous hours of rest, before driving again.
Reality - (more often then not)
Most large cities do not have much truck parking within the city and many businesses do not allow you to arrive early and park in their lots. Your appointment is 8:00am so you leave at 6:00am to arrived your allotted one hour ahead of time. You check in at 7:00am and are told to listen on channel 10. They will call you with instruction when they are ready for you. At about 8:30am you are directed to a dock. By about 11:00am, you are loaded and ready to go.
This leaves you with 9 hours to go about 600 miles. Remember your 14 hours clock started at 6:00am and ends at 8:00pm and you will probably have to park about 50 miles from your destination. This means you would need to drive 66.6 miles per hours for 9 hours straight to arrive 50 miles from your destination by 8:00pm so you could get 10 hours of rest so you can leave at 6:00pm to drive 50 miles so you can arrive at your appointment one hour ahead of time.
First of all you will probably average about 30 mph until you get out of the city. Also not all highways have a 65 mph limit. Many are 55 mph. Even the 65 mph ones frequently have slowdowns for road construction, congestion, or accidents.
Next if you're told it is 650 miles the actual miles will be closer to 700. Most mileage is just a rough guess from city to city and do not take into account the distance from business to business within the city and the longer routes trucks need to take.
If you run legal you will be late!!!
Most of the problem is the conflict between the contacts (shipper/broker, broker/trucking company) and the federal rules the drivers have to abide by. Often the pickup and delivery times are set between the shipper and broker, it then goes to the trucking company. It is possible that the above load could have been delivered on time if the load had been ready to go by 9am, but this variable put the weight of getting the load delivered on time on the drivers and they have no control over.
Delivery appointment should not be set until after the load is loaded and ready to go. Then with information like accurate miles, speed limits, available parking (on or off site), hours available for service, number of load checks/rest stops/lunch break/shower and a possible fuel up, a reasonable delivery time could be set up.