There are a growing number of apps designed to help people find parking, and even reserve and pay for parking in advance. Some know the state of lots. These apps are good for the user but also can produce a public good by reducing the number of people circling looking for parking. Studies suggest in certain circumstances a large fraction of the cars on the road are doing that.

This weekend, I attended the Maker Faire. I've been to almost every Make Faire, including the first, and now it's grown to be far too successful -- you can hardly walk down the aisles at the busy times. They need more space and a way to put more of it outside so thin out the crowds. Still, it is one of those places that makes you feel very clearly you are in the 21st century.

Early on Maker Faire realized it had a parking problem. The lot at the fairgrounds fills up now even before the event opens, and they manage various satellite lots and run shuttle buses to them.

This year they tried something interesting, a twitter feed with parking updates. They tweeted when lots filled up or re-opened, and suggested where to go. They took some limited feedback about lack of shuttles. I think that it by and large worked and reduced traffic around the event.

However, my judgment is that they were not entirely honest in their tweets. This year, and in prior years, they strongly encouraged people to go to one of the most remote lots, regularly telling people it was the fastest route to the event. This was not true. I don't want to ascribe any particular malice here, but there is a suspicion that there is a temptation to make reports in the interest of the event rather than the user. This does have positives, in that cars diverted from near the event reduce traffic which makes the shuttle buses run much faster, but if you give wrong information (deliberately or by accident) this means people stop trusting it and you get the traffic back as more people ignore it.

For example, we stopped at a remote lot, and saw a very long shuttle line. We drove on to a closer lot (also reported as having spaces, but not reported as clearly a better choice) to find lots of spaces, no shuttle line, frequent shuttles and also a walk that was only slightly longer than the shuttle trip. The value of traffic and parking coordination around big events is high, and might justify an app or better tools. Normally I agree with the philosophy that if you can do it with twitter or another existing tool, that's the wise choice. Everybody has twitter. But more sophisticated tools could:

• Load balance, by assigning people to destinations and giving them reservations for a close spot and an earlier shuttle
• Track people (and shuttles) via GPS as they arrive to coordinate them without them doing anything.
• Offer incentives to park in certain locations, including reduced parking, shuttle reservations, admission discounts etc.
• Provide tools for parking workers and shuttle drivers, and even users, to report shuttle line lengths, lot occupancy etc.

Another low-tech idea would be to forbid departure from the venue's own parking lot until well after the event. As noted, in this case the lot fills quickly, and mostly with people who will be staying all day and even later, including booth operators. But the key value here is that if you know nobody is going to leave the lot, there is no chance of getting a space, and people can learn that there is no point in going by the lot to check it out, just in case a space has freed up. That means almost no traffic immediately around the venue except for shuttles and cabs, and so they flow quickly and smoothly.

This costs revenue, since otherwise the lot can sell spots once they are vacated in the middle of the event. However, those very sales are what cause people to come look.

An obvious alternate is to only allow parking in these lots to those who have reserved and paid for a vacated spot. As people leave the premium lot, others on a waiting list who are not yet at the event can be sold those spots on their phones, and they can come in and show the code. Thus traffic would consist only of those with a paid reservation, and not people hunting who would see signs, "Lot full except for prepaid customers."

Indeed, there's no reason the whole premium lot could not be sold this way -- and many venues do indeed have prepaid VIP lots, particularly for sports. With sports generally there are no people leaving mid-game, so the exit policy is only for events like faires which bring people through all day.

To cap it off, a great tool would be bluetooth verification of payment. In such a system, those with a prepaid reservation would have a smartphone app. As they approached the lot gate, their phone would communicate their code to the worker over BT, and the worker's device would show them as clear, and they would be waved through without stopping for the fastest possible filling of the lot. (An earlier checkpoint might allow customers to confirm their code is working so they can divert to customer service before blocking the entrance line.)

The remaining hard question is how to get the money to pay for all this technology. Obviously if you allow higher charges for parking or fewer staff that justifies the cost. If you allow easy re-sale of spaces that are vacated, that can justify the system. Typically satellite parking lots are free (to encourage their use) so you can't give much further incentive there or provide revenue for justification of the technology.