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.

If your city isn’t meeting your needs, just hack it. Urban hacktivism is a form of creative, citizen-led problem solving that often goes behind the backs of officials and institutions to get things done. Instead of leaving the task of shaping a given city to governments and developers, who tend to ignore the input of people they’re supposed to be serving, urban hacktivists take matters into their own hands by combining crowdsourced knowledge and skills with cheap, readily available materials. That might mean transforming a long-vacant lot into a neighborhood park, adding public seating to an area where it’s lacking, enhancing the safety of intersections for pedestrians or just making urban environments feel more responsive and fun.

At the heart of this kind of guerrilla urbanism is the ability to see the potential of public spaces to better meet people’s needs, make small changes and possibly convince local governments to make those changes permanent in the process. After all, the people who use those spaces every day know best. If you’re interested in carrying out some DIY urbanism in your own city, the internet is full of examples, guides and tutorials to get you started. These hacks may or may not be legal where you live – whether you choose to find a way around that is up to you, and most of these tools come with an obligatory disclaimer that they’re not suggesting, teaching or condoning any kind of illegal action.

Create DIY Crosswalks

Sometimes, cities just don’t seem to know where crosswalks belong. Maybe they’re not paying attention. Maybe there’s some kind of red tape involved. But a lack of proper crossings can be dangerous for pedestrians who simply aren’t going to take a stupidly long way around. If there’s a common crossing near you that isn’t marked, you can mark it yourself, whether by grabbing some paint and forming your own urban repair squad or setting up a temporary illuminated crosswalk, as laid out at Instructables. For guidance on paint selection and other aspects of this task, check out the Tactical Urbanist’s Guide To Getting it Done, a free resource you can download packed with tips for all sorts of projects.

Customize Street Signs

PHOTOS: These hacked electronic street signs make being stuck in traffic worth it http://t.co/XZkdOV8RdJ pic.twitter.com/pu9sFIx9eJ

— RYOT (@ThisIsRYOT) March 13, 2014

Some cities don’t have enough navigation signs to guide people to significant destinations. Some just aren’t adequately marked, like a misleading exit sign over the 110 freeway in Los Angeles, which one intrepid urban hacker fixed himself with a very convincing facsimile of official Caltrans signage (it stayed up for over eight years.) Street artists frequently “hack” signs just to make them more interesting and fun. And, just to say, electronic road signs are pretty easy to hack into just for the sake of making someone smile on their crappy commute, though of course you should never tamper with these signs, as instructions to do exactly that will warn you.

You can also produce your own street signs that look official at a glance, but actually spread positive messages in unexpected places. Seattle-based guerrilla artist April Soetarman sells her own rugged heavy-duty laminated aluminum signs that say things like “NOTICE: I never stopped loving you. I hope you’re well.” It’s easy to order your own custom street signs through any number of websites, all just a Google away, or you can do it through the Walk Your City Project, which links informational street signs “with web-based campaign management and data collection to complement traditional approaches to way finding.”

Hack Bus Shelter Advertisements

Brandalism, “a revolt against the corporate control of culture and space” by an international collective of artists, wants to help you intervene into ad spaces that usually celebrate consumption in favor of art, political messaging or whatever you’d rather look at instead. Carefully noting that the tools they offer “are handmade art objects and not intended for use,” the group maintains a site called PublicAdCampaign.com illustrating the types of tools required to get into bus shelter ads in various cities across the world. You can purchase these tools – er, art objects – directly from the website.

Build Your Own Bike Lanes

A lack of proper bike lanes is dangerous for everyone on the road, whether you’re a cyclist or a motorist. DIY bike lanes are almost always illegal, but that doesn’t stop people from making them anyway in a form of political vandalism that often forces officials to sit up and pay attention. The tactic can definitely pay off, as it’s not unusual for these temporary lanes – made of traffic cones, flower pots, or even toilet plungers – to eventually become permanent. Tactical Urbanism has a variety of tips in this area, along with case studies that show how it worked out in various cities.

Make Modular Structures Out of Found Objects

Hacking cities needn’t (and arguably shouldn’t) involve the purchase of expensive, heavy, potentially waste-producing materials. DIY urbanists are encouraged, instead, to “hack” into existing modular systems to make them work for new purposes. Examples include Mifactori’s “Circular Street Waste” workshop, in which discarded furniture and other trash collected from the city streets is transformed into versatile multi-use parts that could become tables, benches, shelters and more.

Similarly, the 3erlin Grid (say “Berlin Grid”) offers a grid-based decentralized open standard for building objects and structures that always leaves a distance of 3cm between holes for nuts and bolts so all parts always fit together and can be combined in infinite ways. So if one person builds, say, a DIY table for a city, someone else can come along and add to it. They’re often based on children’s toys, found objects that can be easily modified, like fencing and scaffolding. The principles follow those of OpenStructures, which include using recyclable materials, designing for disassembly and making components as cross-compatible as possible.

Many tactical urbanism projects are self-explanatory, and easy to recreate just by looking at what other people have accomplished. Check out some of our previous posts on urban hacking for a whole lot of inspiration.

Tactical Urbanism: 15 Low-Cost City Hacks for Fun & Functionality

The Rotten Apple Project: Quick & Dirty Urban Hacks

City Hacktivism: 12 Fun DIY Urban Interventions

Hack Your City: Guerrilla Grafter’s Guide for Making Ornamental Trees Edible

Street Re-View: Hacking Google with Theatrical Performances

Abandoned Bridge Amphitheater Reclaims Public Space

This vast volume full of mixed watercolor swatches and other illustrations elaborating explains the art and science of combining waters and colors to create a huge array of tones, tints, shades and hues.

Created by artist  A. Boogert, this Dutch book is one-of-a-kind, a unique handmade production designed to educate students and artists about how to mix, make and deploy individual colors and color schemes. The entire work is thoroughly indexed and each process described in impressive detail.

Medieval book historian Erik Kwakkel considers it a comprehensive coloring guide ahead of its time. “I encountered this Dutch book from 1692 in a French database today and it turns out to be quite special. For one thing, no Dutch scholar appears to have published on it, or even to know about it. Moreover, the object is special because it provides an unusual peek into the workshop of 17th-century painters and illustrators.”

More from the aforementioned scholar: “In the 17th century, an age known as the Golden Age of Dutch Painting, this manual would have hit the right spot. It makes sense, then, that the author explains in the introduction that he wrote the book for educational purposes. Remarkably, because the manual is written by hand and therefore literally one of a kind, it did not get the reach among painters – or attention among modern art historians – it deserves.”

If you want to see the volume yourself: Aix-en-Provence, Bibliothèque municipale/Bibliothèque Méjanes, MS 1389 (1228). Luckily, the entire book can be viewed here, in hi-res, zoomable images. Here is a description of the book. Thanks to the internet, this single-run work now finally has a shot at the global audience for which it was intended (via Colossal).

Created by Le Corbusier, one of the most famous architects of the Modern movement, this vintage Polychromie Architecturale: Die Farbenklaviaturen book features interactive pop-up and pull-out pages to illustrate ideal color combinations for architectural and interior designers.

Developed for and published by a Swiss wallpaper company, a rare first edition of the 1931 original volume is being auctioned in New York, its paper sliding elements and color sample storage pockets still functional and intact.

Like much of his work, which treated architecture as “machines for living in,” Le Corbusier saw color as something that could be systematized for the modern era. These, in turn, could effect the health and happiness of building occupants. His polychromatic custom color systems included a “color keyboard” for matching hues and shades across the spectrum.

Also as with his other systematic efforts, Corbu boiled down color selection to key components like mental effects, weight and depth, perception and unity – these parallel the logical and reductive approach of his “five points” for designing architecture. Color combinations were designed to take advantage of the positive potential in mixing and matching.

Lighter and more natural colors could warm rooms while darker shades could camouflage parts of a space. He also designed wallpapers that took his color theories into account, combining them with rational geometries to form modern patterns. Despite the rarity of the volume and fame of its author it is expected to sell for only a few thousand dollars at the Swann Auction Galleries.

Nothing gets lost in translation with these embedded English pronunciations, tied directly into the Japanese typographic style Katakana. While the letterforms of Katakana create an effectively phonetic alphabet, its characters are still difficult for some foreigners to read, at least until now.

Like many design solutions, this one looks easy in retrospect: simply tuck an English-legible phonetic articulation guide using a capped alphabet inside the Japanese characters. The result: Phonetikana, a potentially very powerful tool for communication, teaching and learning, or even signage in places like international airports or multinational conventions.

From the creators: “Multiple trips to Japan and constant frustration at being unable to read the language has sparked off an unusual typographic project at johnson banks. Earlier in the year we started seeing if we could combine the English language and Japanese script in some way.”

The firm went a step further as well, embedding words and phrases inside symbols to create a children-legible introductory guide to Japanese, reinforcing connections between each sound and symbol set. Meanwhile, the hybrid typography remains a work in progress, but definitely on the right linguistic track.