Some suggestions from Kunos:
change slightly the value of the sun direction
change ambient light to grey. choose the best tone for your scene. White light will have a flat illumination on your track, while grey will enhance your details.
Of course you can experiment the way you like to have the effect you want.

You can change the ambient light color double clicking on the rectangle as shown in the picture below




Similar settings can be done on each material in your track.
If you will find a good guide on phong shading, and ambient, diffuse, specular settings, please add some informations here.

Here is the way to fix the problem of shining hills:
set specular to black

ccool