When running down the road, you should always run facing traffic (except where local laws state otherwise) because it is much safer for you. Any time that you are a pedestrian and are not on a sidewalk or crosswalk, then you should be facing traffic.
You want to run facing traffic because…
- …you will know when somebody is coming.
- …two heads will have an opportunity to avoid a collision (you and the driver).
- …in some areas, it is illegal to run or walk with traffic at your back.
- …if everybody did this, then you would not have to worry about passing somebody going in the other direction while two cars are also vying for road real estate at the same time.
- …drivers expect you to be running towards them and predictability makes you safer.
When I plan my routes, I try to make them go in a (generally) counter-clockwise direction so that I will be facing traffic as I run and will not have to cross traffic (at least, on this side of the pond). When I can find trails, I prefer to take them as it takes traffic directly out of the equation.
If you are on a sidewalk or trail, then you should run on the right side, however. This will make it less confusing if you are passing cyclists, rollerbladers, or other pedestrians. Again, predictability will make you safer.