I have filmed a car-ride and want to spice it up using Adobe Premiere Pro 7.0. I want to speed up the clip, so it looks like I am driving very fast. This was no problem using the "speed/duration" option, but I want it to gradually increase speed from normal to 450% of the original, so it will look like I start driving at normal speed and then accelerate to 500km/h!!!!

I tried to cut the clip in several small portions and then increasing speed by 50% for each small clip but this gives me a jerky transition which I'm not satisfied with.

I can't find anything on this in the Premiere help function, so I hope someone out there can help me.