public interface ISomething {

}

​

public interface ITransport<out T> where T : ISomething

{

}

​

public class Transport<T> : ITransport<T> where T: ISomething

{

}

​

public class Potatoes : ISomething {

}

​

public class Route 

{

  ITransport<ISomething> Transport;

  public Route(ITransport<ISomething> t)

  {

    Transport = t;

   }

}

​

public class Program

{

    public static void Main()

    {

        Transport<Potatoes> myTransport = null /* or getAllPotatoes */;   

        Route myRoute = new Route(myTransport);

    }

}