You're able to see fine because the streets are lit. If it's an unlit MUP path, that dinky little LED isn't gonna cut it. In fact, 30mph = 44 ft/sec. I'd like to think at that speed, you can't even stop in 3 seconds but I'll give 3 seconds of warning anyway, which is 132ft.

The 3 LED's from the cateye el320 can barely light up a reflector from half a football field away, let alone let you know if the road is even there at that distance.