You can customize routes generated by MileOn by editing your trip settings in the Trip Settings menu.  (Premium only)

Tap the gear icon at the bottom of the Plan screen to open the Trip Settings menu.

Avoid Tolls

Tap the toggle button to have MileOn generate routes that will avoid long stretches of toll roads but will not take long, impractical detours to avoid toll bridges and tunnels. 

HazMat Restrictions

Tap the down arrow and select any hazmat restrictions that apply to your vehicle. MileOn will generate a route for hazardous materials. 

Tap Done to apply these setting to your trip.