Izmit is a city in Turkey. Izmit rarely sees many tourists, however, it is on an important junction involving the E881 (Bursa and the west coast) and the O-4/E80 (heading towards Ankara and the north east).
Note that cars heading from Istanbul to Bursa (or vice-versa) rarely passby Izmit due to the Yavlova-Gebze ferry.
Sneaking onto the O-4 is the best option if you want to head a long distance towards Ankara or Samsun. There is the trucker's parking stop about 1 hours walk uphill north-west from the town centre near the "Tepe Ustu mosque/cami". There is a fence around the highway and the truck stop, however, there are many openings in the fence. Once in the truck stop just flash your thumb around and you should get a ride in a short time.
The walk is a long one although there are buses from the town centre for 2 TL.
One could also hitchhike next to the bus station on the ramp heading towards the highway, however there is a chance that you may be told to go away by the police. The location itself isn't great either since it lacks a place for the driver to stop efficently. Should you choose this option it is recommended that you use a sign since the ramp leads onto both directions of the highway.