In a lot of ways, a recumbent bike can be safer. You're lower to the ground, so there's not as far to fall in the event of a crash. You also aren't going to flip over the handlebars the same way that you would on a normal bicycle. And that's not even looking at the reduced stress over time on your back and spine.
However, there are a few ways in which these bikes can increase the risks when you're riding around traffic.
The lower stature of the bike does make it less likely that drivers will see you. It's already hard for them to spot bikes, and being just a few inches off the pavement can make you nearly invisible.
Some have said that it's not the car right behind you that's an issue. That driver will see you. It's that the car behind that car may not. So, if you have a steady line of traffic overtaking you, one car after another, you're at risk that a driver will eventually fail to see you pedaling along in the bike lane or on the side of the road. This could cause an accident.
There is also something of a learning curve. A recumbent bike does not turn the same way as a standard bike. The center of gravity is different. It stops far differently. These are things you need to learn slowly and with practice, and it may be best to do that when there is not any traffic around.
If you are hit while riding a recumbent bike, make sure you know all of the rights you may have to financial compensation.
Source: FindLaw, "Can I Sue for a Recumbent Bike Accident?," Ephrat Livni, accessed Nov. 27, 2017