In Norway, from Oslo to Trondheim is about 500 kilometers (310 miles). There are several transportation options: air, train, car, bus or even ship. Each transportation mode has pros and cons, though, so take a look and pick the one that's best for you to get from Oslo in the south to Trondheim in the north, or vice versa.
Oslo to Trondheim by Air
Starting at around $175 round-trip, this isn't the cheapest option to get from Oslo to Trondheim, but with a 60-minute duration, it's definitely the fastest.
Note that it's cheaper to fly from Moss Airport or Sandefjord Airport outside Oslo, instead of using Oslo Gardermoen Airport. SAS, Widerøe Airlines, and Norwegian Air have many direct flights between Oslo and Trondheim daily.
Oslo to Trondheim by Train
It's a scenic seven-hour journey if you take the train from Oslo to Trondheim, or from Trondheim back down to Oslo. The train ticket just about equals the flight price, from approximately $150 for date-flexible, round-trip tickets. There are three to four train connections daily, and you can buy train tickets online. It may be a little slower, but this is definitely one of the more relaxing ways to spend your travel time between these two destinations.
Oslo to Trondheim by Car
If you're renting a car while in Norway, you can just drive from Oslo and Trondheim. The trip is quite doable and doesn't require a whole lot of directions (or even GPS).
Between Trondheim and Oslo, it's about a 6.5-hour trip (500 kilometers/300 miles) by car. There are two options for the drive, as follows:
You can take E6 all the way, going through Ringsaker and Folldal. Make sure to check traffic if you end up using this route in or out of the city in the morning or late afternoon in order to avoid rush-hour traffic.
The shorter route, which is Rv3 through Elverum and Alvdal, saves about 30 minutes of drive time but can get you stuck behind slower vehicles on the country roads. When leaving the city area of either Oslo or Trondheim on E6, simply look for Rv3 for the shortcut. It is definitely a little more scenic than E6, but your overall speed won't be as fast.
Oslo to Trondheim by Bus
Traveling by bus is a cheap option, and with a travel time of around eight hours, it doesn't take much longer than driving yourself. The NOR-WAY Bussekspress bus #135 (known as the Østerdal Express) leaves from Oslo Gardermoen Airport. Each way there are two bus connections daily, one in the morning and one at night. For this mode of transportation, which is by far the cheapest, one-way tickets cost around $25.
Oslo to Trondheim by Ship
If you have more than four days to journey from Oslo to Trondheim and want to go the most scenic way, try the Hurtigruten & Norway in a Nutshell tour. Don't forget your camera, especially in early and mid-summer. You'll be traveling by boat and train between the cities of Oslo, Bergen, Trondheim, and Hurtigruten. Disadvantage: The high price of about $550 a person (and higher depending on room choice) and the possibility of the weather in Norway not cooperating.
Also, if you get seasick easily, this might not be the best option for you.