Communication between moving vehicles during the narrow window of the late 1990s

The long holiday weekend in the United States means that there are probably going to be a lot of people on road trips.

Back in the old days before mobile phones, if you had multiple cars traveling together on a long trip, you had to stay within visible range of each other so that you didn't get separated. And if the car at the end of the convoy needed to pull over to take a bathroom break or something, they needed to rush to the front of the group and pantomime through the window to the passengers in the lead car to tell them what they were going to do, and then everybody would pull over together.

I still remember those days.

Of course, nowadays, you'd just whip out your mobile phone and call the other people in the group. "Hey, we need to stop for a bathroom break. You can join us, or we'll just catch up with you down the road."

There was a narrow window of a few years where WiFi hardware was generally available, if somewhat expensive (in the form of a PCMCIA PC Card for your laptop and a $1000 base station)¹ and mobile phone coverage along highways in less populated areas was spotty or nonexistent. That was the window of time during which I wrote a chat program for multi-car road trips.

The idea was that we would establish an ad-hoc wireless network among the laptops, and the program would act as a peer-to-peer instant messaging program. We would be the world's fastest-moving WiFi hotspot. As long as the cars stayed within around 100 meters of each other, we would (presumably) still have connectivity. The program was robust to outages, and it could handle devices dynamically coming into or leaving communication range.

With this technological contraption, we didn't have to make everybody stop and pull over in order to decide where to have lunch. We could just start an IM conversation and work it out while still moving. (But if we wanted to take a bathroom break, everybody had to stop; otherwise the cars would get out of range.)

I over-engineered this program, designing it to handle chats that if printed out would require a roll of paper over 300 kilometers long. In other words, for a 300km trip, you would have to be sending instant messages fast enough that you could drive on the paper coming out of the printer. (Related.) Another way of doing the math was observing that the program could in theory handle a cross-country trip where people were sending 500 messages per second the entire time. (Well, except it would have run out of memory long before hitting its design limits.)

This program met an even sadder fate than my in-car mp3 player. At least I got to use that program a few times. Mobile phone technology quickly improved to the point where the car chat program was no longer necessary. It was never used at all!

¹ I still have my $1000 base station packed in a box somewhere. I wouldn't be surprised if my my mobile phone now has a faster data plan than that thing.

Comments (39)
  1. Rick Glorie says:

    I am impressed with your solution, but wouldn't walky-talkies have worked? I know people who still use those.

    [But I don't know how to build a walkie-talkie. Also: TECHNOLOGY. -Raymond]
  2. Sean says:

    I don't entirely understand why you can't get separated. Why not just make sure every car knows where they're going (and the planned way to get there), and all set off independently? You don't really need to all have lunch together, nor do you have to coordinate bathroom breaks. Doing it that way seems a lot easier than any of the solutions you've described.

    [I guess you are content to sit in one car with the same people for the entire trip. Some people like to mix things up and change cars every few hours. That way, you get a chance to talk to everybody eventually. Also, you all arrive at the same time, even if there are unexpected snags like a road construction detour. -Raymond]
  3. voo says:

    @Sean Yeah all this pesky "doing a trip together" stuff really only complicates things. Personally I find everybody tells the others where they're going and then they do completely separate things really cuts down on all this organisational problems ;)

    Personally walky-talkies are the best solution there, cheap, good enough range and exceedingly fun to boot!

  4. Boris says:

    What about hand signs out of a window?


    …to which the reply would be:


    …or, in unusual circumstances:


    [What's the hand sign for "How do you turn on the air conditioning in this car?" -Raymond]
  5. Boris says:

    (The software didn't render thumb-up and thumb-down.)

  6. Rick C says:

    "I guess you are content to sit in one car with the same people for the entire trip."  There is an obvious solution, but in light of your ridiculous objection to walkie-talkies, you clearly wanted to roll your own.

  7. Ken Hagan says:

    I have had the chance to try much the same thing more recently. The kids' Nintendo DS-es have no mobile connection of their own but will happily connect to a portable WiFi hotspot. In practice, however, the Faraday cage effect of your average vehicle means that such hot-spots are considerably smaller than the 100m you mention.

    So it is probably just as well that you didn't ever use it.

  8. Smeargle235 says:

    The one time I was on a trip like that, we used MURS radios to communicate between the cars, which worked out surprisingly well.

  9. Capi says:

    Why is everybody arguing over why Raymond did this? It's obvious: because he could! Kudos to that! And it seems like exactly the thing I'd really have used back then.

    [Also: Because we all already owned laptops. None of us owned walkie talkies or CB radios. -Raymond]
  10. pete.d says:

    Clearly, the point here was simply to show that it could be done. And kudos on that point.  :)

    Prior to MURS (those long-range walkie-talkies you can get…approved by the FCC in 2000…they can also be hooked to an external antenna for improved range), there were CBs. Those worked fine for vehicle-to-vehicle communication, and had better range than even MURS would. While MURS is not quite as long-range as CB, both are still _well_ over the 100 meter mark. Miles of range in good conditions.

    In all cases (CB, MURS, wifi), a convoy still needs a contingency plan in case of separation (or one passenger disabling the communications device on purpose…as happened to me on a trip long ago), generally of the form of "we will meet at this well-known chain of restaurants/hotels/etc. [preferably where there's likely to just be one or two in any given town]". The current technology — cellular phones — are much better in this regard, allowing way more flexibility and last-minute arrangements/negotiations. But phone batteries still can run out, there might be gaps in coverage (especially on a road-trip, which often take people outside of the densely inhabited areas), or any number of other things could happen to render the phone inoperative.


    So, no…no one ever needed a rolling wifi network. We've always had better communications options, at least during the era when wifi was conceivable. But none are as technically challenging and interesting in getting a technology totally not intended for this purpose, to work for this purpose.

    Where's the fun in taking something off the shelf that is already designed to do exactly what you want it to do, when you can cobble together an inferior solution from more expensive parts? :)

  11. Viila says:

    I was expecting the related link to rather point to What If #11, since it mentioned physical relationship between miles per gallon and units of area. Driving at the speed of printing seems like similar comparison.

  12. ErikF says:

    I think that having a DAN (driving area network) sounds like a great thing! Imagine being able to play multiplayer games in LAN mode between cars. The only issue is the sun, glare and bouncy roads making game control a little difficult.

  13. Mark Y. says:

    You can still use this program to save on roaming charges! :)

  14. j b says:

    I am impressed by your design!

    But, going back a few decenniums: When I was living in the US in the late 1970s, "CB radios" were on the rise to becoming super popular. Everyone wanted them in their cars, and in their homes for communicating with their cars. (Call them "walkie-talkies", if you like, but that term halfway suggest that you brought them with you when you were out walking.) I had the impression that their popularity were strongly increasing in the 1980s, and you more or less expected the car in front of you to respond on the CB radio if you called him up to tell him that his left braking light was not working, or something like that.

    Then: At what time did they turn into something outdated, the kind of stuff only old people cared about, or whatever was the reason for their decline? I didn't realize they were gone until… well, must have been early this millennium. Maybe they had been gone for a long time then. Are anyone at all using CB radios in the US nowadays, or are CB radios something only grandpas have a vague memory of?

  15. Joshua says:

    I have frequent occasion to drive roads where cell coverage still doesn't work. Occasionally we do in fact have chains of more than one vehicle. But yeah walkie-talkies are readily available.

  16. CatCube says:

    @j b

    There are plenty of people using CB, though it has gone by the wayside.  CB was the nontechnical and nonlicensed subset of Amateur Radio, which was more or less what computer geeks did before computers were invented.  (If you want a technical hobby that's not computers, I'll give that a shoutout–at 32, I'm often the youngest guy at Ham events and we could use the new blood.)  Once better communications options appeared, it sucked the life out of the radio hobbies.

    A big thing now is packet radio (APRS), which does more or less what Raymond was attempting here, but using radios capable of miles rather than meters, and using a repeater system.  You could use a mobile Ham radio on 144.390 MHz to transmit the data, but FCC restrictions limit the bandwidth immensely–only 9600 bps is possible in the 12kHz-wide channel.  If you did need more than that, using a wireless router in the UHF band, which has much wider bandwidth.

  17. Engywuck says:

    @Ken Hagan: you probably cannot count an ordinary car as a faraday cage in wifi frequency ranges. 2.4GHz frequency is equivalent to 12.5cm (ca. 5 inches) wavelength and a car has many openings far wider than that. Cellular phones use even lower frequencies (and therefore larger wavelengths, down to 700MHz/230cm(92 inches)) and you still can use them while sitting in the passenger part of the vehicle.

    Sure, an external antenna probably would be better, but several dozen meters should be possible, if not drowned by other sources.

  18. j b says:


    Actually, I have been holding a ham license for forty years, but haven't been on the air for more than thirty. When I started out, you could transmit digital data, provided they were Baudot coded text. Not ASCII. but that age old, five bit character code (I think the formal identification is ITA2). You had to use a (locking) shift code even for a full stop, and of course digits. The PTT insisted on being able to automatically log anything that we transmitted on the amateur bands, and in the 1970s and 80s, their automatic equipment couldn't handle ASCII… (I don't think they ever logged anything, they just insisted on having the ability.)

  19. acq says:

    @Engywuck, Karl actually tried to do what he describes, and you armchair philosophies that he's wrong. I still believe you're wrong and he's right. He tried it. You just expect something based on your understanding. Well try it now first and then tell us your findings.

  20. Yair says:

    At a conference I was at once, there were two buses full of programmers going to a party. Someone suggested that we could set up ad-hoc Wi-Fi networks between the buses to facilitate communication, but that we should make sure that we have very good drivers, because these would be high-throughput networked buses.

  21. smf says:

    "The idea was that we would establish an ad-hoc wireless network among the laptops"

    What is the $1000 base station for if you're using an ad-hoc network?

    In light of the PCMCIA to PC Card change, are you sure it was Wi-Fi? 802.11b was released in mid 1999, but the Wi-Fi name appears to have been introduced in 2000. Either your narrow window was in a different decade or you need to clarify what hardware you had.

    [The base station is for getting wireless Internet access in my house. I mentioned the base station to provide historical context, not because it was part of the solution. -Raymond]
  22. Ben Cooke says:

    I am on such a trip right now and argued that forming and maintaining a convoy wasn't worth the effort. I was overruled at first but out car is about to arrive alone after we lost track of the last member of the group. So much simpler now.

  23. Boris says:

    What about renting a minivan? No possibility of separation (not ever), no communication issues, flexible seating arrangements…

    [I don't think there's a minivan that holds 14 people. -Raymond]
  24. dave says:

    >What about renting a minivan?

    It doesn't scale.

  25. Dave Bacher says:

    In the early/mid 90's, I worked on a packet radio transceiver on an ISA card that went physically inside a PC/XT or AT.  We had a 286 laptop with two ISA slots, and we'd use that for demos.  That'd get you a cool 1200 baud connection shared with anyone else on the same channel, using a protocol that is the great grand-daddy of GSM today.

    That, in normal conditions, can reach 44 miles.

    Provided both parties are licensed hams.  That would have been cheaper than your base station, I want to say we retailed at $459 but it's been a while.  You'd have to add an antenna on top of that, but that'd let your program reach much farther for the proposed use, at a lower cost than the contemporary wifi.

    And 1200 baud isn't speedy — but it is plenty fast for most IRC sessions.

  26. Theo says:

    [But I don't know how to build a walkie-talkie. Also: TECHNOLOGY. -Raymond]

    Can't think of a better answer then that.

  27. SimonRev says:

    Laptop with 2 ISA slots:  I once had an old 286 computer that shared an owners manual with that PC manufacturer's "portable" 286 computer line.  However at 33 pounds with an integrated 7 inch CRT display I wouldn't really call such a device a laptop.  (I think the 33 pounds was without the optional hard drive which would have added a few more pounds)

  28. Gabe says:

    The original version of 802.11 (before 802.11b) was only 1MBps or 2MBps and could use frequency-hopping spread-spectrum. Some implementations of that had a range of 2000 outdoors, but I'm not sure if "between multiple cars" counts as "outdoors".

  29. morlamweb says:

    @Boris: Sometimes a little separation is a good thing on long road trips…  When I had to do long road trips for work, I'd take a rental car whenever possible, so that it would take the beating (and maintenance requirements) and not my personal car.

  30. Dave Bacher says:

    I want to say it was a Franklin, it's been a while, but it looked like their Apple II compatible portables.

    It had a 14" clamshell, sitting on top of a 3" deep base.  Something like 88% keys.  Behind the screen, it got deeper, and the ISA cards were mounted horizontally.  They had to be half-width ISA cards, because the power supply filled the other half.  The monitor was glorious in 16 shade of green glory against a light grey background, with a response time such that directory listings showed as solid green boxes for several seconds after you typed the command before the pixels settled.

    But it looked a lot more like a laptop than the luggables did, and wasn't nearly as heavy as a luggable.  

  31. > I don't think there's a minivan that holds 14 people. -Raymond

    Not with that attitude.

  32. Boris says:

    Maybe not a minivan, but a 14-seater van definitely exists according to the search engine of your choice. And only one person need drive at a time instead of four?, so you can rotate every now and then. Although a special driving license seems to be required, that would only be a one-time investment, assuming the group of travelers is fairly consistent.

    [On the other hand, not everybody is comfortable driving a 14-seater van (I sure wouldn't be), parking is difficult, and it means that you can't have "Day 3: Everybody does their own thing." As evidence, I also call your attention to the fact that you pretty much never see a 14-seater van on the highway. -Raymond]
  33. Brian_EE says:

    @Boris: But then you are stuck in that one vehicle with all 14 people the entire time. That seems like a good enough reason to take a few smaller vehicles.

  34. Boris says:

    @Brian: perhaps, but if I didn't feel like sitting with them for hours on end, then once we'd arrived at our destination, would I be in the mood to partake in several days of shared lunches, dinners, tourism? I don't think so; in both cases, it would have to be a closely-knit group, not merely casual acquaintances who in some cases may only tolerate each other for another's sake.

  35. Nico says:

    For a moment at the start of this post I thought you were going to say you used the fairly common infrared sensors that used to decorate laptops.  I had a brief vision of a convoy of cars, each with a powerful IR LED transceiver array mounted to the roof, with fiber optic cables going down into the cabin and attached to the infrared port on the laptop.

    I have no idea what kind of range you could expect to get out of such a system without fancy hardware or optics sitting between the laptop and rooftop LED, but the absurd mental picture makes me smile :)

    A potential issue I see with your WiFi proposal is the 100m range.  60 mph is about 27 meters per second, so a maximum range of 100m means the cars must be withing about a 3.7 second following distance (75 mph drops it to 3 seconds).  Not unreasonable for a brief message exchange perhaps, but it might be asking a bit much for anything much longer.

    Still, a neat idea that would have been very cool to see in action!

    [I think special relativity says that it's only the relative speed between sender and receiver that matters. (Attenuation due to increased medium density is negligible at automotive speeds compared to light speed.) -Raymond]
  36. Engywuck says:

    @acq, at rereading I noticed my error, had read a part of his statement as theoretical instead of "have done it".

    Still a car is no faraday cage (where the signal loss would be (near) total, but of course all the steel, people inside etc. do quite a bit of reflection and attenuation. Having the antennas near the windshield and the rear, respectively, should diminish the problem a bit (as of course would do base stations in each car with external antenna). But probably a tiny bit too costly at the end of the 90s.

  37. Erin says:

    We once rented a 12-passenger van for a joint vacation with my brother-in-law and his family.  The 19-hour drive was much more pleasant with 3 drivers instead of 2 and available pre-teens who wanted to amuse the baby.  BIL had rented his own car at the destination, we used the van.  And you actually do see quite a few of them in Disney parking.

  38. smf says:

    >The original version of 802.11 (before 802.11b) was only 1MBps or 2MBps

    802.11 was sold under the name WaveLAN. Wi-Fi was created as a friendly name for 802.11b after the standard was published and could only be used for products that had been officially tested. There were problems with 802.11a for a long time, but they've now rolled all the standards up back into 802.11-2007. It's nearly as confusing as all USB products being allowed to be branded as USB2.

  39. cheong00 says:

    I think my father got his set of walkie-talkie from hiking equipment store in Hong Kong. It is one of the standard equipment for more advanced level of hiking here (They don't necessary walk the paths there, they may climb through a few cliffs by ropes on they way.)

    While Hong Kong is one of the place that you got highest level of mobile coverage here, there are still places like deep in the hills that got no signal. In such place walkie-talkie still works fine when you get nothing blocking between the teams.

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