They have LEDs inside and out. The exterior ones appear to be the same displays as used on 168s and 170s
A way to tell whether you are looking at an LED or flipdot display is to see what happens if you take a photo of it. Have a look at this image from the front of a bus, taken from my collection:
Notice how there are thin lines across the text on the display, which are not present to someone looking at the display in person.
This is an artefact of the way the vast majority of dot matrix displays work. Rather than illuminate every line at once, they switch between which line is illuminated extremely quickly. This is a simplistic description, but the fine details aren't really relevant here. What's notable is that there is no point at which all of the LEDs required to make the image are illuminated at once.
Usually this doesn't matter, because persistence of vision effectively means that our eyes blend it together so we see the complete image. But a camera shutter can be much faster than this, and if it is, then it will only be capturing the image for the time that some of the LEDs are illuminated - and hence, some of the LEDs appear off, causing the black lines on the display.
Depending on the display being photographed as well as the camera, this effect can be even worse. This image was taken with my smartphone instead of my proper camera, and is of a different display. This one's broken up a lot more, and appears much worse.
If you're very unlucky, you can actually end up photographing at a point when
none of the LEDs are illuminated, which makes the display appear blank (There was a destination written on here):
It's worth nothing that this test only works one way. If you see this kind of artefact, you can be fairly sure that you are looking at an LED display. However, there are plenty of combinations of display, camera, and camera settings which don't produce this kind of artifact at all. For example, this display produces pretty much no artefacts at all, despite definitely being LED. (Ignore the fact that this particular display is showing incorrect information!)
However, there are other ways of telling what type it is. For example, if the dots that make up the display appear to be turning around when the display changes, that's obviously a flipdot. If the display is able to scroll smoothly, it's definitely LED/