[Note that this article is a transcript of the video embedded above.]

A train is a simple thing at first glance: a locomotive (or several) pull a string of cars along a railroad. But not all those railcars are equal, and there are some fascinating details if you take minute to notice their differences. I’m about to start a deep dive series on railway engineering, but I thought, before I do that, we should cover some of the basics first. How many of these cars have you spotted before? I’m Grady, and this is Practical Engineering. Let’s get started.

All trains have at least one locomotive that provides the power. They can pull from the front (called the head) of the train, push from the tail, or act as so-called distributed power somewhere in between. There’s a ton of types of locomotives, but they deserve their own video, so today I’ll focus mainly on the unpowered cars they push or pull. We’ll start with passenger cars, move on to freight, and then talk about a few of the more unusual cars you might be lucky enough to spot on the rails.

Unless you work in the railroad industry, passenger trains are the only ones you’ll ever get a chance to interact with. The standard passenger car or coach is what you’ve probably seen the most of: aisle in the center with rows of seats on either side. Some coach cars can be disconnected and rearranged, but most modern passenger cars come in “train sets” that are rarely split up in normal operation.

Some passenger cars are bilevel, also called double-decker. This can double the capacity of a car, but it’s kind of rare. That’s not only because of height and weight restrictions on railroads, but also because the added time it takes to load and unload the cars can cause congestion at busy stations.

Long-haul passenger trains may include a baggage car for checked luggage like the cargo hold of an airliner. In most cases, they’re designed to look like the rest of the passenger cars, although often with fewer windows since bags rarely enjoy the view. Combine cars have a section for passengers and one for luggage or freight.

Although tricky to identify from the outside, a common sight on passenger trains is a diner car, essentially a rolling restaurant. These cars gave rise to the quintessential American restaurant of the same name, many of which are converted railcars themselves. Some passenger routes even include a lounge car, a bar on rails, that sometimes even has live music.

If you’re sleepy after dinner, you might find yourself in a sleeper car. Open section cars have the beds in bunks with only a curtain for privacy. Most modern sleeping cars have private rooms and bathrooms akin to rolling hotels.

These days, especially in the US, passenger rail is used by people who find the journey itself to be the destination. Some passenger trains include dome cars for better sightseeing along the trip. A bulbous glass dome provides a panoramic view from the side of the car. Similarly, observation cars are sometimes included at the end of a train to give passengers a view out the back.

Of course, we can’t forget crew cars. All trains have a team of people who work aboard for operation, maintenance, and other tasks, and they sometimes need their own quarters for breaks or sleep. Especially in areas like Australia where there are huge stretches of rail without stops at cities, a whole second crew might wait in the crew car, ready to swap when the working time limits of the first crew are reached.

Passenger trains are cool, of course, but I’m more of a freight train railfan myself. There’s just something awesome about seeing a single car weighing sometimes more than 100 tons move almost effortlessly down the steel rails. And with the huge variety of types of freight that move overland come a huge variety of railcars.

Boxcars are a common sight with their huge sliding doors. They can be loaded by hand or forklift and accommodate a wide range of sizes and types of cargo that require protection from the elements. And they have a few variations too. A refrigerated boxcar is exactly what it sounds like: a giant insulated fridge or freezer on rails. They usually feature a diesel-powered refrigeration system that’s easy to spot from the outside.

If the goods being transported in a boxcar are relatively light, you end up completely filling the car before coming close to its weight capacity, sometimes called “cubing out” the car. To maximize the use of a boxcar for lightweight cargo, there are taller versions called High Cubes. Not all railroads can fit such a tall car because of tunnels or bridges, so you might see the excess height portion of the car marked in white to make sure it doesn’t inadvertently end up on a route without the necessary clearance.

If you want a train car full of cars, then you’re looking for an autorack, designed to carry consumer cars and trucks. Many have three levels and carry dozens of vehicles at once. Freight rail moves automobiles cheaper and with better protection compared to driving each one individually from factories to distribution centers. A few passenger trains pull autoracks as well, like the autotrain between Washington DC and Orlando. You can take your car on your rail trip and have it at your destination.

When it comes to freight cars, it doesn’t get much more straightforward than a flat car. A simple name for a simple function: just a rolling platform that can be used for all sorts of cargo, especially big stuff that needs to be loaded with a hoist or crane and cargo that can handle a little rain or snow. You might see flat cars used to transport heavy equipment and machinery, pipes or steel beams, or even see multiple flat cars outfitted to transport enormous wind turbine blades. Some flatcars feature bulkheads at the front and rear. These help keep loads like steel plates, pipes, and wood products from shifting forwards or backwards when the train accelerates or brakes.

Another flat car variant is the centerbeam car, used to haul lumber, plywood, wallboard and fencing. The central beam helps stiffen the car, making it possible to stack products higher. It also provides a place to secure the loads from either side of the car. Some centerbeam railcars hold enough lumber to frame out half a dozen houses!

Flatcars are also used for intermodal shipping, or using more than one mode of transportation like trucks, trains, and ships. Trailer-on-flatcar, or TOFC, isn’t exactly a distinct type of railcar, but it is a distinct use of one. A semi-trailer is lifted or driven onto a flatcar at one terminal, and it’s ready to connect back to a truck once it reaches the next intermodal facility to be driven to its final destination. This is sometimes called piggy-backing and it can be a cheaper alternative than trucking the trailer for its entire route.

Most intermodal freight these days comes in containers, standardized steel boxes that fit on trucks, trains, and ships. Container-on-flatcar, or COFC, again isn’t a different kind of car but simply a specialized use. The cast corners of steel containers have holes that make them easy to secure with latches or twist lock devices so they can be quickly loaded and unloaded.

One of the great advantages of containerization is that modern intermodal containers can be stacked. An interbox connector slots between the corner castings and holds each box together. But, you don’t see double-stacked containers on flatcars very often, because of height restrictions and issues with center of gravity. Instead, well cars recess the bottom of a container between the wheels, lowering the top of a double-stack and making it safer at speed. Not every line has the clearance, but well cars have made it possible to double-stack intermodal freight on a lot more routes than before.

Coils of sheet metal are used in countless manufacturing processes, so you can see them on freight railroads fairly frequently in coil cars. Steel coils are challenging to load and unload, and challenging to secure as well, so that’s why they get their own specialized cars. Many are covered with a hood to protect the steel or other metal cargo from the elements.

Gondola (GON-dola) cars, or gon-DO-la, depending on where you live, are used for bulk materials like scrap metal, sand, ore, and coal. They’re basically enormous wagons. Gondolas have to be loaded and unloaded from the top with a crane or bucket. Some can be turned upside down and unloaded using a rotary dumper. Look for the different color of paint on the side with the rotary coupler.

Hopper cars are like gondolas in that they’re loaded from the top, but they have sloped sides and bottoms that funnel material so they can be unloaded through hatches at the bottom. Hoppers can have open tops when carrying loads that aren’t sensitive to the weather, but covered hoppers are used for cargo that needs protection from the elements like sugar and grains.

Another option for unloading bulk goods is to tip it sideways. This is a side dump car, not very common to see. They’re mostly used to maintain the railroad itself, rather than move and deliver bulk goods to customers.

This next car is very rare, but it’s so cool I just had to include it. Behold the behemoth that is a Schnabel car. There are actually two cars with far more axles than normal, each sporting a heavy lift arm for truly enormous cargo, such as power transformers used in substations. One of the largest of these is used in the US to transport nuclear reactor containment vessels on 36 axles.

Tank cars are used to carry liquids and gases on rails. Like all railcars, there are plenty of variations, but in general, they’re split up into two types. Non-pressurized tank cars handle all kinds of liquids from milk to oil. They may have specialized coatings that match their specific cargo needs, can be insulated or even refrigerated, and they usually have a bottom outlet so that they can unload by gravity.

Pressurized cars are designed to transport liquids and gases under pressure. These tanks have thicker walls and higher standards for containment of cargo. Pressurized cars always have protective housings covering the fittings on top of the tank. But, some non-pressurized cars have them too, so you'll have to look for other subtle clues (or memorize the DOT classification numbers) to know which type each one is for sure. Tank cars designed for hazardous cargo are heavily regulated and have special features like reinforced ends called head shields, specialized couplings that reduce the impacts of a derailment, and pressure relief valves to minimize the chances of an explosion.

I can’t be totally comprehensive for this short video. If you can dream it, there’s probably a freight railcar of it somewhere, but that should be all of what you’re likely to see in the wild, plus a few that you’d be really lucky to spot. But passenger and freight cars aren't the only things you'll see on the tracks. Non-revenue cars are those used by the railroad companies themselves. After all, building and maintaining railroads is a complicated and expensive endeavor, and it takes a lot of interesting equipment to do it well. I’ll rattle some of these off, but every railroad is different in the type of equipment they use to keep things running smoothly.

Ballast is the name for the gravel bedding that railroad ties sit on. It distributes the enormous pressure of trains to the subgrade, provides lateral support to keep tracks from sliding side-to-side, and facilitates drainage to keep the subgrade from getting soggy. Ballast tampers shake and pack the ballast under the tracks, restoring the support if the ballast has settled and sometimes correcting the rail alignment too. Ballast regulators use blades and brushes to distribute the ballast material evenly around the tracks and keep excess ballast from covering the ties. A ballast cleaner picks up all the rock, separates it from any dirt, and replaces it on the tracks to improve its ability to drain water and lock together to support the railroad.

Rail Grinders do just that: grind the rails to restore their shape and remove irregularities that show up as rails wear down. A tie exchanger takes out the old ties and inserts new ones without having to remove the rails. A spiker drives the spikes that hold the rails tightly to the ties. A railroad crane is used for heavy lifting along the rails where it might be difficult to access with an overland crane. Some railways in the north use a rotary snowplow during severe winter weather to keep the tracks clear.

Sometimes you might see a work truck driving around on regular old paved roads with an extra set of flanged metal wheels. This is a road-rail vehicle also called hi-rail (since they can run both on the highway and the railroad). There’s a whole host of hi-rail vehicles out there, really any kind of work truck setup you can imagine on the highway could find itself doing work on the railroad. And this is probably the only rail vehicle you’ll have a chance of seeing without also seeing a railroad itself!

Railroads depend on large scales to measure the weight of equipment and cargo. And of course, if you’ve got a scale, you need a way to calibrate it, which is where the scale test car comes into play. These cars are basically rolling hunks of metal with very precisely known weights, kind of like a huge railroad version of the little weights you might have used in school science classes.

A particularly rare car that you’d be lucky to see is a track geometry car. They carefully measure the gauge, position, curvature, and alignment of the railroad, helping to ensure the safety and smoothness of tracks without interrupting service. Unlike manual measurements of rail geometry, the measurements of track geometry cars account for loading conditions since the car itself is a full-scale railroad car.

And finally, bringing up the rear, a train car we’ve all heard of, but one you won’t really see too much of any more: the caboose. Historically, cabooses housed crewmembers who had a host of jobs, from helping with switching and shunting cars around, to looking for damaged cars, dangling equipment, monitoring brakeline air pressure, and spotting overheating bearings and axles. With the advent of roller bearings and wayside defect detectors, the role of the caboose was diminished and eventually the laws requiring them on trains were relaxed. Today the last car of a freight train is often just a regular cargo car, but with a small device on the back called an End-Of-Train Device. The most sophisticated versions monitor brake line pressure and movement of the back of the train, relaying the information to the engineer at the head. And a flashing red light lets anyone know that that’s the whole train and there aren’t any cars inadvertently left behind on the tracks.

Trains are one of the most fascinating engineered systems in the world, and they’re out there, right in the open for anyone to have a look! Once you start paying attention, it's pretty satisfying to look for all the different types of railcars that show up on the tracks, and in future videos, I’m going to show you a lot more. If you’ve been inspired to keep your eye out, we put together a checklist that you can use to keep track of the cars you’ve seen. It’s linked below in the description, but that’s not all.

If you’ve watched my channel for any length of time, you know that almost every video I make is connected to something you can see in your own surroundings. You might even know I released a book about it: Engineering in Plain Sight: An Illustrated Field Guide to the Constructed Environment. And now, I’m launching a companion game too. This is Infrastructure Road Trip Bingo. Our brains have a stupendous capacity to ignore all the fascinating details that are hidden in plain sight, and road trips are the perfect opportunity to open your mind’s eye.

Infrastructure Road Trip Bingo is just what it sounds like: a spotting game to play with your fellow passengers. Each sheet has 24 engineered structures that you might see on a typical road trip. Some you’re sure to spot. Some you might need to try and influence the driver to take a special detour. Get a line of 5 before anyone else, and you win. All the icons were designed by the illustrator for my book, and there’s a cross reference table inside the cover if you want to learn more about a particular square. 100 tear-off sheets mean you’ll have plenty of chances to play and win, and the squares are randomized so that no game ends the same.

Is this a silly idea? Of course it is. But, what I’ve learned from you over all these years is that you’re enthusiastic about the built environment just like me. Engineering In Plain Sight hit the Publisher’s Weekly best seller list, and it’s still topping out categories on Amazon nearly a year later. So I wanted to give you a chance to put those observation skills to the test. Infrastructure Road Trip Bingo goes on pre-sale today, only on my website, and they’ll start shipping later this year. And if you still don’t have my book, you can get a copy bundled with your game for a huge discount as well. You can get it from any retailer, but if you buy from my website, I signed every single copy in our warehouse. These are awesome gifts, or treat yourself with something fun and cool, and support what we’re doing on Practical Engineering while you’re at it. That link’s in the description. Thank you for watching, and let me know what you think!