I've created a new blog category "Burning Man" to track my posts on the event. I was using a simpler tag before.

Today I want to talk about the Burning Man Exodus problem, a problem you might find interesting even if you don't come to Burning Man. This year, even at 8pm Monday there was a long line and a 2 hour wait to get off the playa. Normally by about 5pm there is no wait. With 45,000 or more this year, and I presume at least 15,000 to 20,000 vehicles, and various chokepoints limiting traffic to 450 cars/hour, how do you drain the playa when everybody wants to go Sunday and Monday. (In addition, with so many now leaving Sunday, it makes Monday less interesting driving some who could leave Monday to leave earlier.)

It has now been routine to see waits of 5 hours or more at the peak times. I believe a solution should be possible involving some sort of appointment system, where cars are given a set time to leave, and they leave then. If they want to go at a peak time, instead of waiting 5 hours in line, they spend 5 hours in the city, or doing more cleanup, instead of idling their car in a giant line. Not that the line doesn't become a little bit of a party, but it's still not like being in camp. And for my exodus on Monday night there as the worst dust storm ever for Exodus, you could not see the car in front of you, or the fence beside you.

However, a good system to hand out appointments is hard to design. First of all, we have a mostly volunteer crew, and they don't have much law enforcement power to stop violators or ticket them. (More participation by the police in this, when the city truly needs them, instead of having them be there for pot busts that nobody wants would be a great thing.)

Here are some of the constraints: * We don't want to encourage people in any way to rush out of camp to make their appointment, and do less cleanup and in particular not do the final moop check. The current system as the advantage that generally you clean until done, then get in line and wait however long it takes. * We also don't want people to just all try to grab the earliest or choicest departure time "just in case" and instead leave much later. A system that gives you an exit time like "3pm or later" just encourages everybody to grab the earliest time they can, defeating the purpose. * We do have to understand that people will not be perfectly punctual on the playa even when trying hard. * Commerce or special rewards for wealth are frowned upon. I will note later that while an auction system for prime departure times is an interesting solution, it would not jibe well with playa culture. (Though at the same time people in planes get to inherently avoid the lines.) * People will not readily follow rules. To get reliable rule following, police may be needed. * There can be severe weather, where you can't even see 10 feet.

The simple version

What I will describe below will sound complex, but in fact for users it's pretty simple.

• When you arrive, you'll get a card for your vehicle. Follow the instructions on the card, and store it safely. They say...
• When your camp area is fully cleaned, send somebody with the card to one of the stations shown on the map.
• There you'll get a card with a colour, and an exit time, and a map showing you where the lot for your colour is. The card will tell you when's the earliest and latest to show up at the lot mapped on the card, and what roads to take and signs to follow to get there. Listen to Exodus Radio at xx.x FM for any alternations to the plan.
• Show the card to the exodus worker. Tune your radio to the Exodus channel.
• Listen to and obey the Exodus Jockey on the radio. When he says "Green Lot, go," advance with caution in a line at 10mph. If flaggers contradict the EJ, obey the flaggers.
• You will get a $XX traffic ticket for violations of traffic rules that hurt others.
• As you approach the left turn onto the paved road, unless the flagger or EJ is indicating you should stop, safely turn without stopping.
• If you lose your cards, line up the in the lines for people without cards, signs will show you. You'll exit slowly.

But really just "You'll be given a card with exodus instructions when you come in. Keep it and follow them. If you lose it, look for signs."

That's it.

Exit Cards

My proposal starts with an exit card every vehicle gets when it enters the playa. The gate crew would hand out the card and write the car's licence plate on the card with a marker. This means the card can't be traded, but does present problems if it is lost. However, it is not useful to steal -- so put in in a safe place in the car. This card should not be easy to forge. Gold foil stamp or unique paper would work.

Exit Appointment

An exit card is not an exit appointment, but it can be traded for one. We would need stations at some key points in the city (3, 6 and 9 plazas, perhaps more) where a person could come on a bike with their exit card. An exodus staffer would then give them their exit appointment. There would perhaps be 3 blocks of 20 minutes per hour. The red block would be at the top of the hour, the blue block at 20 minutes past, and the green block and 40 minutes past. At 10am you might get handed a 2:20 pm appointment card, which would be blue, with a big "2PM" on it. It would also have a foil stamp or other hard to forge design, and your licence plate would again be written on it with marker.

There would be 3 staging lots, marked red, blue and green. Each lot would handle 150 vehicles in perhaps 3 lanes of 50 each or similar configuration.

Exit Radio

A radio station would be dedicated to exit. Aside from telling people the current wait time for appointments, and wait time for people leaving without appointments, it would actually marshal the cars. People without a car radio would be asked to bring a small radio. This might be an AM station or a new use for an old FM station. An FCC licence might be needed, alas. The Exodus Jockey (EJ) would control the exodus.

After the 1:20 pm crowd cleared the blue lot, the exodus worker would close the exit with cones and radio the EJ, who would tell people with blue "2" cards that they could move to that lot. At the front, an exodus worker would open the entrance to the blue lot, and wave in cars, doing quick checks of appointment cards which should be clearly shown in the windshield. Random spot checks for forgeries would be done. People with forged cards would be sent to police. People with the wrong cards might just be turned back or also sent to a holding lot or to police. Signs would be telling people to listen to the EJ and not to enter a lot without the right card. Well before the worker a sign would warn "If you don't have a blue card with the upcoming hour and your licence plate on it, turn back now or get a ticket." Another sign would say "We mean it."

Time to go

When we are ready to empty the staging lot, the EJ would ask the worker to remove the cones in front of lane 1, and tell all drivers in lane 1 to start moving at once at 5mph, and proceed to the blacktop. They would be reminded at the blacktop to not stop for the left turn as long as the flagger there is waving them on. (A flagger at the turn onto the blacktop road waves traffic through except in the rare times when a non-BM car is coming down the road, and then the BM cars have to stop briefly.)

It might be possible for the EJ to even control the line of cars as a unit. With signals from the flagger all cars could be asked to brake at once, and start up again at once, instead of the slow system where you do this based on watching the car in front of you and their brake lights. Not that you can't watch that, but we might get something closer to a train.)

Not everybody will make their appointment, and so the blue lot may empty before 2:40 and the green lot's turn. Here, I see two options. We might allow the green lot to start moving early, though people would still be entering it. However, that would make an even bigger gap as the green lot would empty well before 3:00.

As such there would be another line, similar to today's line, for cars who missed their appointment, or who have no appointment. That line would feed into a 4th lot, the yellow lot. In a suitable gap, the yellow lot cars would be allowed to stream out.

Missed appointments

There are several ways we could deal with missed appointments. One would be to be strict, and simply tell people to line up with those who have no appointment. Another would be to cut some slack and allow at least a few such cars to go in the next batch for their colour (ie. in one hour) with a little extra capacity in each lot for such people. Another would be to have the first lane in the yellow lot be for people with missed appointments.

As noted, the more you punish a missed appointment, the more likely it is that people will rush out of camp, leaving a mess for their friends or for clean-up crew. So you can't punish missed appointments too much. I suspect the priority position in the yellow lot (or simply yet a different lot which has this position) is the right approach.

Appointments well in advance

Another option is handing out appointments well in advance, even before the event, with the most popular times allocated by a lottery. In this case, missed appointments become important. If there is little penalty for missing an appointment, everybody will just take the earliest appointment. If there is a heavy penalty, people will not clean up properly. What might make sense -- but requires more manpower -- is a penalty which varies based on how much you miss it.

For example, most people should be clear that they will miss their appointment some time in advance. If you are in camp 1 hour from appointment and you have 3 hours cleanup to do, you should go and change your appointment. There will be no shortage of people to take your slot, and you could get priority on a new spot 3 hours in the future. This requires a bike ride to an Exodus station of course.

Missing an appointment by a few hours might result in a small extra wait. However there could be a threshold of about 6 hours which is treated like not having an appointment at all. (This prevents people from asking for noon Sunday and really leaving Monday.)

However, my experience is that people are not good at predicting when they will be clean, so I suspect making appointments long in advance will have too many problems.

Random instant exit

Alternately, many people, hearing the current delay is 4 hours, will go get an appointment for 4 hours in the future because they think they have 4 hours of cleaning left to do. This will lead to people misjudging that time, and rushing off. One idea to deal with this and assure that people only take appointments when they are cleaned up and would otherwise have entered the existing long line is to have a little lottery. When they go to get their appointment, there is a small chance they would be told, "You won. You're leaving now" and be handed a special card for immediate exit. If they really are all cleaned up, they would say "great" and drive out. If not, they might fess up, or they might clean up and thus leave from the yellow lot. Or they might decide to just leave the cleaning to their campmates. If they are the last to leave their camp (rare during the peak hours) it is unlikely they would just leave gear on the ground. However, I can also say camps just having an agreement saying "If anybody gets instant exit, take it, we'll bring the rest of your stuff, you promise to do the same for us" so this might not work. I am open to other suggestions.

Bidding

In a capitalist world, the problem could be solved by people bidding for the prime times in a 2nd price auction. The money would go to reduce everybody's ticket price. But that's not the way Burning Man works, is it?

As I noted, this is a hard problem, but there has to be a better solution than everybody just getting into a 5 hour line and inching forward in stop and go traffic.