I am stuck behind the road fence, and I can't jump over it. Help!

The first time I played this game, I somehow "glitched" to the other side of the fence, around the area with the gate thingy. But, I can't make myself glitch outside again...

You're not supposed to be able to jump; if you head forwards from the car you come to an overpass with a streetlight on the left and gate on the right. The gate is closed until you near the streetlight, at which point the sky gets darker and the gate opens - then you can explore the surrounding areas.