Most cities have so much in common that a generic “map of every city” can seem similarly familiar to people living in London, Paris, New York or another metropolis entirely. General types of neighborhoods aren’t the only things different cities share, though — much less obvious but pervasive are sets of codes, symbols and markings that can communicate meaning across different times and urban spaces.

Even though (or perhaps because) people drive over and walk by them every day, it is easy to overlook the rich, colorful and cryptic utility markings spray-painted onto streets and sidewalks. Like graffiti tags or hobo codes, this language of scribbled text, dots, lines and arrows may seem indecipherable at first, but lives depend on engineers, city workers and utility companies understanding what they mean.

Utility markings tell excavators working on subsurface projects where to dig and (more importantly) where not to dig. A vocabulary of symbols (with its associated grammar of colors) helps diggers steer clear of dangerous power, sewer and water lines as well as other pipes and cables.

Like any language, utility codes have evolved what one could call regional “accents” of a sort — linguistic conventions that vary from one state or country to the next. Standardization, though, is important in helping keep people safe, which is why there are often local or national rules governing what different colors and symbols represent.

Long before cities came around to the idea of utility markings, train-hopping nomads were working out similarly symbol-based systems of communication. As these travelers roamed America looking for work, particularly during the Great Depression, they learned to leave messages for one another — so-called “hobo codes.” These relatively simple symbols could help fellow travelers find good places to camp and kind people who might give them meals, for instance.

At the time, being nomadic was a mixed bag — some travelers were known as bums or tramps, disparaged for drinking or idling rather than working. The term hobo, though, was more specifically applied to those actively seeking work and willing to take on jobs others didn’t want to do — hobos were met with various degrees of caution and generosity. Many were illiterate, however, so coded symbols with intuitive meanings helped them convey messages through etched or chalked markings. The relatively discreet size and abstract shapes made these marks easy for people not in the know to overlook.

Some symbols represented fairly specific suggestions about how to behave and what to avoid. A cross, for instance, could indicate that talking about religion might help a person get free food from a particular resident. Other markings might caution hobos about heightened crackdowns on vagrants and beggars by local police. While train-jumping culture has changed, some modern travelers have attempted to digitize the idea of hobo symbols through QR codes.

Mural and graffiti art sit somewhere between officially sanctioned and illicit urban communication, depending on the location and surface being tagged. These interventions, too, have evolved a lot over the years. Definitions and genres have sprung up along the way, helpful for tracking and analyzing but also understanding different works — there are pieces, tags, stickers (or: slaps), throw-ups, stencils, heavens, blockbusters, wildstyles and more.

A piece, for instance (short for “masterpiece”) and is usually a complex and multicolored affair difficult to do illegally given the time they take to make. A blockbuster can go either way, often made using rollers and designed to cover up a surface — sometimes one that has already been tagged. A heaven, however, is generally illegal, defined by the difficulty of putting a work up high on something like the back (or front) of a highway sign or the surface of a billboard advertisement — not generally places where one can get official approval to paint.

Some typologies are pretty self-explanatory, like bubble letters or fat caps, the latter of which are usually done with wide spray tips, making them both easy to deploy and easy to read (in turn rendering them useful for get-in-and-out-quickly situations). Shadow letters can also take a bit more work, but help a tag pop off a surface, giving it a somewhat more weighty and three-dimensional appearance. Indirectly, the forms and shapes of letters and symbols tell the observer something about the artist’s intent and constraints. Graffiti can even be broken down into characters, alphabets and fonts, which an informed onlooker can use to better understand a given work.

Some artists and art fans have gone to great lengths to classify different types of graffiti, but such a task is destined to be forever incomplete — graffiti is personal and location-specific, not based on any shared font or type. But some, like artist Evan Roth, try anyway to collect, identify and compare examples of letters, creating order out of the seeming chaos of conflicting tags. He also took his project full circle by pasting up alphabets along the city blocks in which they were originally found, encouraging people to look at tags in a new light, offering temporary glimpses into the linguistic ties that bind them loosely together. With any street communication, legal or illegal, there will always be some give and take between fluid creativity and efforts to categorize, standardize and simply understand.

Traveling light takes on new meaning when jumping trains, as does the limited battery life of mobile devices – just like the rest of us, hitchhikers and train hoppers these days increasingly see the web as as invaluable resource. The underlying story of nomadic life on the rails is surprisingly consistent in some ways: people, generally young, using the nation’s railways to travel the country. The details are, however, revealingly different – analog hobo codes have given way to digital hobo coders.

Like many 30-somethings, Huck has experienced life with and without a pervasive internet that answers all questions. This transitional generation knows to rely on conventional knowledge and hard research as much as spoon-fed answers. In the extended interview below, this reddit user (/u/huckstah) and long-time /r/vagabond participant shares stories from his nomadic lifestyle. Images here by Molly Steele illustrate some of the everyday wonders of illicit train travel as well. Per Hobos of Instagram , these travelers are trading their flip phones for iPhones, starting Instagram accounts … and bringing an age-old tradition of trainhopping and tramping into the Information Age.”

Online resources provide help in all kinds of ways, including some websites dedicated to helping the (often intentionally) homeless and misfit travelers as they hitchhike or dumpster dive. At the same time, there are many ways to also turn ordinary resources toward new ends, like using Google Maps to scout the layouts of train yards for security gaps and best access points.

Beyond transit, maps are also helpful for finding public restrooms, camp grounds, power outlets, showers and other essentials. Kindles (or other devices using less power than phones) are critical to stretching battery life, too. Ultimately, the information flows both ways: travelers turn around and share their adventures on Instagram, Vine, Facebook and other social media sites.

Those on the road more often than not find themselves looking for remote digital work or seasonal employment, again aided in part by websites like Craigslist and otherwise. YouTube videos help guide people through various processes of actually getting on and off trains, as well as finding the best boxcars on (or in) which to travel. Of course, none of these reduce the real, physical-world risks and dangers associated with train hopping, including but not limited to injury and arrest. Some naturally worry that the spread of this form of transit to the internet will increasingly lure people who are not equipped for the lifestyle to try things better off watched on Vimeo or read on reddit.

An estimated 100 million people worldwide are “homeless” … but what is homelessness? Is a squatter homeless? What about someone who stays in a shelter each night? A Web Urbanist article on creatively designed homeless dwellings and nomadic urbanism sparked a lively debate on this subject, which ended up being far longer than the article itself. However, each commenter seemed to understand the nature and problems of homelessness in a different way. Everyone knows that there are people on the streets without a choice as well as nomadic cultures and migrant workers. Few people realize, though, how many nomadic urbanists there are – those who choose atypical ways of dwelling (within or between cities) that involve no fixed residence.

Car Living is becoming increasingly popular out of choice or necessity as the cost of living increases in major urban areas. The above image was taken under a bridge in Seattle, and depicts one of the many semi-permanent dwellings found there. The graffiti on the side shows how the resident has essentially painted a ‘front yard’ on the trailer, a symbol of ‘home.’ Those living in this area appreciate the lack of rent and relative quiet of Seattle’s Industrial District. While the city officially discourages these nomadic dwellers, there are no residential neighbors to complain so they are largely left alone.

Couch Surfing is very different kind of urban nomadism. People from around the world use various related forums and websites as they travel in order to stay free and meet new people. Couch Surfing dot Com has over 250,000 registered users and boasts available couches in virtually every major city in the world. In theory, a person could live from couch to couch indefinitely. Couch Surfers rely on reviews of one another and of places to stay, so maintaining good behavior is rewarded with better future couch surfing opportunities.

Architects, designers and urbanites are becoming increasingly interested in nomadic building design, from shipping container museums to portable temporary housing. Homelessness, in many ways, is a descriptive term that could be applied to more and more of the world’s population. There are certainly many people who did not choose and do not wish to remain homeless. Still, it is important to remember that the word ‘homeless’ carries many connotations that may or may not apply to everyone without a home, such as car dwellers, couch surfers and other urban nomads.