It is the fourth largest city in Turkey with a population of 2.6 million people.
It is beneath Mount Uludağ, a popular ski resort.
Take the Bursaray metro to Küçük Sanayi* and walk around until you find a suitable place to hitch (you would have to exit the south side to reach the pedestrian bridge to the gas station westwards or see below about next station). Although, one hitchhiker experienced that in the end of july 2014, a lady came up and told him that the cars passing by only went for factories and homes(?) and not exactly the way to Izmir. She advised him to find another place or go to the busstation and take a bus, and after he went to the busstation he was guided back to the same spot, only a little further, from which he stood an hour before a pick-up - which isn't normal in Turkey.
If you are able, find a ride to Minteks Tekstil/Restaurant which is at the merging of the D200 and O-5 increasing your chances. However, there doesn't appear to be any public transport to there, no minibus that I asked would go there.
- [experience] I found upon arriving at this station that the metro continues and turns right blocking your path West to get to the gas station, so you end up walking to the next station Altinsehir and crossing under, adding another 20-25min walk. So you might as well go straight through to there, then walk through the industrial yard. Much closer. That said I had bad luck, waiting over one hour.
The road out of town towards Istanbul doesn't have many places where a car can safely pull over so you may have to wait, by turkish standards, a fair amount of time. When you do get picked up you're likely to be given a ride to Gemlik or Orhangazi rather than directly to Istanbul.
One good thing to do is try to get past the highway which runs west to east about 10 km north of town. A lot of traffic comes through this road en-route to Istanbul from cities in the south and if you stand after the intersection your chances of finding a direct ride to Istanbul increases vastly.
An unorthodox way of getting to Istanbul that User:Damaniacle discovered was to hitch to Mudanya (take the Bursaray to Organize Sanayi and hitch from there) and busk at the entrance to the terminal, with a little sign saying that you don't have enough money to pay the ticket. within three songs he had the necessary 22TL (although sometimes it is 27TL - that is the student price, but they luckily didn't ask for proof). the workers were supportive, and gave him a cup of tea. boat takes one and a half hours, and arrives in Yenikapı.
Take the metro to the last stop Kestel. From there you are directly at the main road (Ankara Yolu Cd., D200) which takes you east out of the city. A lot of people go to Inegöl from there, but you can also find people who go further. Cars drive very fast there, so it can be a bit tricky to find a good spot where people can pull over.
Alot of traffic coming to Bursa from Istanbul takes the Eskihisar car-ferry to Yalova (the ferry is easily hitchhiked just follow the instructions on the Eskihisar page) It's really easy to just ask around in the ferry for a car going directly to Bursa (atleat 50% of the cars on the ferry go there). Otherwise you could go around the bay of Izmit although it generally takes more time.
The bus system and Bursaray metro system costs 2TL for a single ticket. A card can be bought for 3.50TL or you can borrow one. With a card it costs 1.25TL, and can be used for more than one person at a time. Each station has a security guard with a metal detector and it seems quite difficult to blackride unless you are super sneaky.