Walking is, and will remain for the foreseeable future, the main way of trans-versing the world.
A dog pulled travois is beginning to replace wearable computers as the required personal accessory. Canines have a number of useful attributes, even even when they're not being used for transit. Hunting to supplement food, keen ears to warn of danger, warmth and companionship are all noble traits. Their size means its easier to protect them by bring them inside a shelter, and transport if a vehicle is found. Furthermore, a lot more people are capable of caring for dogs than large farm animals.
Speaking of dogs, cats and terriers are also common pets - because they hunt common pests, rather than their use for transit.
Horses and other draft animals are rarely used in the zone. Not many people have the resources to care for them, and such large creatures are rather inconvenient when scavenging in a city. Given that 90% of the US population was living in cites - riding animals for extended periods could be considered a lost art. Furthermore, there is the difficult process of taming a wild animal, as most of the domesticated ones are gone. They might have starved in their paddocks when their handlers disappeared, or escaped to the country side and reverted to their wild state. Rumors persist that reanimated animals exist. While there was certainly heavy usage of nano-medicine in some animals, nothing has confirmed these stories so far.
Animal powered farming is making a small comeback, but machines are far preferred even when considering fuel shortages - they don't get sick, go lame, while allowing a greater amount of territory can be cultivated. Unfortunately, without GPS satellites in orbit, they tend not to work as automated units like before - but some creative people have set up transponders to get around this, adding yet another advantage.
Other Transit Means
In some places electric or high-speed rail lines are still functional. The USA took a while to introduce fast train service, but was a few branches eventually materialized. The main ones are:
- Colonial Road: a straight shot up and down the east coast from Florida to New York
- Death Valley Express: California, Nevada, Texas - wider gauge, slower, and optimized for cargo, provides the east coast access to the Gulf of Mexico without needing a ship to go through the panama canal.
- "Chi-Ny": NEST 2 in New York state (but not far from the city) to Chicago
- Winter Line: Trans-Canada rail, not actually connected to US system however.
Following older rail lines is still a common tactic amongst scavengers, as they obviously lead somewhere, and rail hub warehouses are often full of useful supplies.
Although bikes might be limited, motorcycles offer speed, fuel economy, and the ability to maneuver around abandoned vehicles making them quite popular.
Military Multi-fuel vehicles are a two edged sword. Their ability to run on even the poorest home-refined products is a great boon, as is their rugged construction. On board electronics including internally guided navigation systems, night vision, drone support, military map databases, and powerful radios are all much sought after (and more likely to have been emp shielded than their civilian counterparts). Unfortunately, the many powerful abilities make them so sought after they often end up stolen either when the owners are away or when the original users are liquidated. Some people have taken to explicitly avoiding military gear because its used as bait in traps, or attract the wrong kind of attention.
Military exoskeletons are unlikely to be used as transport. Although designed to simplify long marches, most of the ability is due to weigh distribution systems, making a heavy load seem much lighter, but not adding speed, or making normal walking any less tiring. Despite their environmental systems wearing one for more than a few a dozen hours will rapidly lead to chafing and discomfort. Without charging their fuel cells every two or three days, they rapidly become immobile.
The few cars and trucks that are still working are often used in a convoy manner - some running, others being towed. Mobile fuel processing plants are sometimes employed, but more often a central base is established, scouts are sent out, and then the group exploits from there.