If you have a car or truck and are travelling through an area of dense zombie infestation, you may consider modifying your vehicle. These modifications can make your vehicle more defensible, more deadly to the living dead or more useful.
Defensive Modifications[]
Chainlink Fencing- Cover your windows, sunroof or lights to make it harder to be smashed in by zombies or bandits.
Metal Plating- Reinforce your car. However, added weight may slow your car and reduce fuel efficiency.
Spotlights- Useful for navigating or maneuvering at night.
Steel Bars- Cover your car grill to increase the ability of your car to break through debris.
Plexiglass Windows: Much stronger than normal window glass.
Paint - Covering your vehicle's windows with paint will prevent zombies from seeing you inside. Useful if you want to camp out inside your vehicle. A downside is that you won't be able to see outside the windows. To fix this you can leave a small part of the window unpainted, allowing people inside to peek through it.
Paint can also be used to camoflage your car. Painting the whole car a dark colour will make you almost invisible when travelling at night.
Offensive Modifications[]
Bumper Guards- Adds extra ramming power, and can be modified with spikes.
V-Plow- Can break through roadblocks, fences and the undead with ease.
Sunroof- Provides a space for an armed survivor to get a good shot without difficulty, and is also an extra escape hatch.
Utilitarian[]
Bike Rack- For carrying bikes to use in case the car or truck breaks down.
Roof Rack- Can hold extra supplies
Studded Tires- Breaks through the inevitable mud, snow or ice you will encounter on the road.
Small Raintank- To collect extra drinking water while travelling. Good for nomads.
Extra Fuel Tank- Holds fuel for the road so you won't be caught empty.
Also check out-http://zombie.wikia.com/wiki/Transportation#Improvised_vehicles
It is highly recommended that you watch this-https://www.youtube.com/watch?v=iS8KXHBCimo