There are actually two ways to reach Ivarstead from Whiterun, and if one follows the road signs they may find themselves taking the long way around the mountain. This route is potentially very dangerous for lower level players, as they must pass by a bandit tower (and deal with its occupants one way or another) and then likely encounter opposition such as Saber Tooth Cats as they get closer to Ivarstead itself.
A much shorter (and safer) path would be to instead travel east directly through Helgen where the Dragonborn first escaped after nearly being executed by the Imperial Legion. Note that the grounds will now be occupied by a small number of bandits. This route will cut through the southern foot of the Throat of the World and eventually lead to the crossroads just west of Ivarstead.