Travelers driving from Split to Dubrovnik now have 2 options: a new highway (toll road) or the main coastal road. The highway is not heavily trafficked and generally offers fast, smooth traveling for most of the way (but minimal views). However, when leaving Split drivers have to go about 1/2 hour inland to pick-up the highway. The one-lane coastal road can be much slower, especially in the summer months, but it begins right in Split and offers spectacular sea views. The coast road is very curvy and it is possible to get stuck behind slow moving vehicles for miles. The roads meet up again close to the city of Ploce and the last 1 to 1.5 hours of the trip must be done on the coastal road. Depending on traffic on the coastal road, the trip from Split to Dubrovnik takes approximately the same amount of time either way: 3.5 to 4.5 hours.
Most people use Google maps for directions, and unfortunately they are not accurate. Google maps indicates that drivers have to take a ferry because Google does not include roads in Bosnia. In fact, the drive is quite simple. The main coastal road passes through a small part of Bosnia and then re-enters Croatia a few miles later, with no need for a ferry. Cars that choose the 'transit' lane are generally not stopped at the border crossings, but it is best to have your passports ready for inspection just in case.
In Bosnia, drivers will pass through the small city of Neum. Neum is a market town with lots of shops and a few restaurants and cafes. It is a nice place to stop for lunch or for a coffee. Prices will be in Bosnian Mark, the local currency, but Kuna is widely accepted.