Submitted by brad on Thu, 2006-01-05 17:08.
We risked running low on fuel today, and saw the car sputter briefly while going up a hill. Made it to the gas station fine, in fact with a gallon to spare, it seems.
I presume the gas lines in this car drain from one low spot in the gas tank, but when it's on a slope and very low, there's no fuel there. Why can't we have a series of drains at both back and front (and even all 4 corner points.) It would have to go down from there to stop air getting into the fuel line from the exposed fuel outlet, which may be the reason this isn't done, since the tank is usually down low for various good reasons. Could a smart valve allow for any hose exposed to air to close so that air doesn't get in the line?
I guess stalling going up a hill might not be the end of the world in most places, since you can go down to a flat part and start again, but in a "U" you would be trapped.
Submitted by brad on Sat, 2005-12-31 14:03.
I’ve written before about automatic self-driving cars, both their risks (overregulation due to fear of their use by terrorists) and possible driving forces (oil companies excited by people taking longer trips) and more.
Generally, except for a few specialized applications (such as the automatic parking lot) such cars, if they are to be used where people or cars that may not under network control are present, must start with a basic ability to avoid accidents. In a vigourous debate with friend Charles Merriam last night, the question came up about where the value will lie. Charles is a big proponent of worrying first about crash-avoiding cars.
Right now we all pay from $250 to $500 per year, and often much more, for insurance to cover the risk of accidents. Of course, that’s just the financial cost, and financial proxies for suffering, so the real value we would put on an accident resistent car might be much higher. Perhaps $5,000 to $10,000 over the life of the car.
That seems like a highly lucrative market on its own. While the self-driving car has many other long term merits (because you can do other work while moving, and you don’t have to park it, and it can appear on demand as a taxi for you) we should be very close to financially justifying the accident-avoiding car today… read more »
Submitted by brad on Sun, 2005-12-04 20:46.
I’ve been thinking more about environmental economics since I blogged about retail carbon credits. I was surprised about how cheap (some would say unrealisticly cheap) wholesale credits are — about $2.20 per tonne of CO2. (Update: This price keeps changing. The U.S. price is clearly out of whack down to just 25 cents per tonne in 2009. The European price has declined too, from $20/tonne when I wrote this to $14/tonne in fall 2009.)
Today, many of my friends have bought a car like the Toyota Prius, feeling they are doing their bit to help the environment by burning less gas. The Prius costs around $3,000-$6,000 more than a comparable old-style engine car (in part because high demand keeps the price high), and the savings on gasoline don’t justify it on a financial basis unless you do nothing but drive all day. So the main reason to buy it is to help the environment and to make a statement before your peer group. The Camry Hybrid, which gets 32mpg instead of 23mpg costs about $5,000 more than the regular Camry.)
Problem is, there’s an argument that you’re hurting the environment, counterintuitive as that sounds. And no, it’s not just the unanswered questions about recycling the fancy batteries in the Prius when they fade, where fairly positive results have been returned so far. Read on… read more »
Submitted by brad on Wed, 2005-11-02 13:10.
After we picked up our rental car in Darwin in the Northern Territory of Australia, the blasting heat told us we would like a cooler full of drinks on our 3 day road trip through the outback. So we stopped at a Woolworths and picked up one of those terrible foam coolers, ice and some drinks. There was no bar code on the cooler so we wasted what seemed like 10 minutes in the checkout because the clerk wasn't authorized to ring up an item as general merchandise. (Hint to stores: I know you're scared of your cashiers stealing from you but this is ridiculous.)
It seemed to me that with a sizeable number of the renters in Darwin going off on outback road trips, who among them wouldn't want a cooler. So the rental company should offer a cooler pre-loaded with ice, and even perhaps some drinks. They would of course overprice this, but as long as it's not more than buying a decent cooler, people would go for it over those cheap ones, that can't keep ice long and run a risk of leaking into the nice rental cars in any event. There's other stuff that could go into the road-trip kit, ranging from walkie-talkies to umbrellas to snacks, too.
Submitted by brad on Tue, 2005-11-01 15:59.
You may have heard of the idea of pollution credit trading. I’ve been pointed to two firms that are selling CO2 credits on the retail level for individuals, to offset the output from driving a car, heating a house etc.
I’ll get into the details on how it works a bit below, but if you have a car like mine that is putting out 5 metric tons of CO2 each year, you can for a low price (about $50, which includes a whopping markup) pay a factory somewhere to cut their own output by 5 tons, meaning that net, you are causing zero emissions. Which means you are reducing total emissions by a lot more than you would by switching to a Prius, and you are doing it at a vastly lower cost. (This doesn’t mean you shouldn’t drive a Prius, it just means this is a lot more effective.)
Normally pollution credits are traded only by the big boys, trading contracts with hundreds or thousands of tonnes of emissions. The retail firms are letting small players get in the game.
This is a fabulous idea, in theory at least, and also a great, if sneaky gift idea. After all, if you buy the gift of not polluting for your loved one all they get is a bumper sticker and a good feeling. At least it’s better than giving to The Human Fund in their name.
Here’s the catch. I went and priced the credits, and while www.certifiedcleancar.com wanted $50 to credit my car, the actual price of credits on the Chicago Climate Exchange is about $2.16 per tonne of CO2, or about $8 for my actual output as they calculated it. One expects some markup, of course, and even some profit for the company selling the retail credits, but this is nuts. I called the other company, Terrapass and got reasonably frank answers. First of all, they claim they invest more in wind power and other truly non-polluting forms of energy more than they just buy carbon credits. Secondly, this is still a small volume thing, and most of the costs are not the credits, but the $20,000 or so to become a member of the exchange, or so I was told. And of course, in small volumes, administrative costs can swamp the real costs.
Another outfit I found is carbonfund.org which is non-profit and cheaper. In some sense since people buy these out of guilt rather than compulsion (they were meant to be forced on polluters to give money to non polluters and make a market) non-profit might make sense, but they are also supposed to be a real market.
Still, if I pay $50, I would love for my $50 to mostly go to reducing pollution, not mostly to administration. Usually when exchanges are expensive there are members who will trade for you at much more modest markups. The folks at Terrapass said they were not yet profitable at the current prices.
And it is such a good idea. Read below for more on pollution credits. read more »
Submitted by brad on Mon, 2005-10-24 14:31.
Recently I purchased an external battery for my Thinkpad. The internal batteries were getting weaker, and I also needed something for the 14 hour overseas flights. I picked up a generic one on eBay, a 17 volt battery with about 110 watt-hours, for about $120. It's very small, and only about 1.5 lbs. Very impressive for the money. (When these things first came out they had half the capacity and cost more like $300.)
There are downsides to an external: The laptop doesn't know how much charge is in the battery and doesn't charge it. You need an external charger. My battery came with its own very tiny charger which is quite slow (it takes almost a day to recharge from a full discharge.) The battery has its own basic guage built in, however. An external is not as efficient as an internal (you convert the 17v to the laptop's internal voltage and you also do wasteful charging of the laptop's internal if it is not full, though you can remove the internal at the risk of a sudden cutoff should you get to the end of the external's life.)
However, the plus is around 9 to 10 hours of life in a small, cheap package, plus the life of your laptop's internal battery. About all you need for any flight or long day's work.
It's so nice that in fact I think it's a meaningful alternative to the power jacks found on some airlines, usually only in business class. I bought an airline adapter a few years ago for a similar price to this battery, and even when I have flown in business class, half the time the power jack has not been working properly. Some airlines have power in coach but it's rare. And it costs a lot of money for the airlines to fit these 80 watt jacks in lots of seat, especially with all the safety regs on airlines.
I think it might make more sense for airlines to just offer these sorts of batteries, either free or for a cheap rental fee. Cheaper for them and for passengers than the power jacks. (Admittedly the airline adapter I bought has seen much more use as a car and RV adapter.) Of course they do need to offer a few different voltages (most laptops can take a range) but passengers could reserve a battery with their flight reservation to be sure they get the right one.
It would be even cheaper for airlines to offer sealed lead-acid batteries. You can buy (not rent) an SLA with over 200 watt-hours (more than you need for any flight) for under $20! The downside is they are very heavy (17lbs) but if you only have to carry it onto the plane from the gate this may not be a giant barrier.
Of course, what would be great would be a standard power plug on laptops for external batteries, where the laptop could use the power directly, and measure and charge the external. Right now the battery is the first part to fail in a laptop, and as such you want to replace batteries at different times from laptops. This new external should last me into my next laptop if it is a similar voltage.
Submitted by brad on Fri, 2005-09-30 16:08.
Recently, I discovered something that others have known for a while but many don’t know. Namely that effectively all modern cars that say they should use Premium (high-octane) gasoline run perfectly fine on regular. Since the early 90s, cars have had more advanced carb/fuel-injector systems which adjust to the octane of the gas and don’t knock. Like an idiot, I’ve been filling my car with premium. The engineers at all the major car vendors have confirmed this.
I worked out that since the USA uses 370 million gallons of gas a day, or 135 billion per year, at 12% premium sales, that’s 16 billion gallons of premium sold, almost none of it needed. Call it 15B gallons. At a surcharge of 20 to 30 cents/gallon that’s over 3 billion extra dollars charged to no purpose in the USA, and presumably another 3 billion outside (though perhaps they buy less hi-test outside.) The USA uses about 44% of world gasoline.
So why do many cars come with a line in the owner’s manual saying to use premium gasoline? Turns out the marketing departments believe customers of higher-end cars are ethralled by horsepower. They want to advertise the highest peak horsepower number they can. And you can deliver a slightly higher peak horsepower on higher octane. Nothing so big that you would notice it outside of extreme driving conditions or pro racing, but you can publish a higher number. So long as you spec the car as using premium.
So to satisfy these marketing numbers, the world is spending about 6 billion extra bucks each year on high octane fuel. And I’m not even considering all the extra infrastructure required (fancier pumps and blending systems, more tanks with risk to leak into the ground etc.)
Many people think high-octane gasoline is “more powerful.” In fact, oddly, the octane rating measures how non-explosive the fuel is. The higher the octane, the less likely it will explode under pressure. People think of high-octane fuel as more powerful because with high octane fuel, you can design a higher performance car that works at higher compression, safe in the knowledge you won’t get explosions from anything but the spark plug, ie. knocking. The fuel is not higher power, it’s the engine, which is why putting premium into a regular car is a waste unless it’s knocking. Lead cheaply reduces knocking at low pressure which is why they used to add it until they realized, “holy crap, we’re filling our fuel with toxic lead!”
There is still controversy over whether high-compression engines get better mileage than when they run at lower compression with regular.
What a scam. Spread the word.
Submitted by brad on Fri, 2005-09-23 16:31.
Many are commenting on the gasoline shortages and price increases involved with hurricane evacuation and other emergencies. Some people can’t get gas to get out of the city. Others full up giant tanks even when they don’t need it. Stations raise prices as supply drops and demand increases, as per the normal rules of the market. Some suggest the stations be price-controlled to stop this, but that would only result in even more gas hoarding by the public.
The government could instead have a strategic emergency gasoline reserve. However, it need not keep this reserve in tanks, it could “keep” it in the storage tanks of all the private gas stations, by arranging a special emergency-based futures contract with the station owners, in advance. Not all stations need participate, as long as enough gas for evacuation can be reserved.
During the emergency, it would be calculated how much fuel will be needed per vehicle. Each station would provide that much fuel to each vehicle. The simplest way to do this is to devise some long-lasting mark that will last at least a few days to a week, and for each station to put it on a car after delivering the fuel. Perhaps something as simple as a sharpie mark or other semi-permanent mark on the gas cap. This is unfair in that people with multiple cars could get extra fuel, but other systems, like vouchers and databases have their own problems. Vouchers would be lost or sold on the black market, unfortunately.
Any fuel over and above the contracted amount could be sold at market prices to those who want more fuel and/or wish to hoard. Probably quite high market prices. Fuel tankers could also be arranged to resupply stations with emergency reserve needs. Note that the customers could still pay a normal price for the reserve gas, reducing the cost of the contract. They would also sign a voucher at the station, on which random audits could later be done to confirm compliance. Stations would contract to deliver based on the minimum reserve they keep in their own tanks. There could also be a true reserve in government owned tankers to cover the slop factor.
Submitted by brad on Tue, 2005-09-13 18:43.
Every time I take an RV trip (ie. each Burning Man) I come up with more observations. The biggest one is that it cost $360 in gasoline to go from the bay area to the black rock desert, about 800 miles. And that’s at a price still well below world price. The RV owner said he was planning to get out of the business, people no longer want to pay the gas price.
So why is it taking so long to produce a hybrid RV? Hybrid cars are great of course, but trucks and RVs are what really suck gas and need the improved efficiency. And they have the room for larger and more unusual engine configurations. Most of all, RVs also mostly come with expensive generators and batteries, and a hybrid RV would of course have a super duper power plant and batteries and inverters, presuming the engine was efficient at lower revs. The Hybrid RV’s power plant could also be a backup generator when parked at the non-moving home. Probably make the most sense with diesel fuel, or as I have suggested before, even the highly efficient stirling engine. (Stirlings are big, and take time to warm up, but an RV with batteries is fine with this.)
Every RV’s shower has this hose based showerhead with an on-off dial with a slight leak. Our camp built a much nicer shower using a standard kitchen sprayer. A kitchen sprayer with a lock-on would be much better and would make it easier to conserve water by letting you pulse water where you need it when rinsing.
Cleaning the RV, especially when back from the desert, is hard. RV renters charge fat cleaning deposits and fees. Why doesn’t some company that hires out housekeepers do an RV service. You could come to them. Drive in, and a team of 5 attacks your RV, cleaning it in minutes. Do it at a car wash to also handle the outside if needed. Espcially after Burning Man there’s a business here.
I’ve said these before: Paper towel racks, built-in soap dispensers, inverters, flourescent lights. Why aren’t these everywhere in the RV world, instead of being rare?
Stabilizers jacks are great, but how about something simpler, some way to lock the springs or shocks (of course with an interlock to prevent starting the vehicle!) And while slide-outs are great, why do we never see flip out beds the way pop-top campers have, or a pop-up on the cab-over bed? (Most RVs don’t have any spare wall space except in the master bedroom, which does limit the flip-out bed concept. You also almost never see murphy beds.) Flip-out beds don’t take away your dinette or couch as do the extra beds commonly found. And how about a seat belt design for use on the beds for safe sleeping while driving? You can do this now but it doesn’t seem super safe.
Submitted by brad on Sat, 2005-08-13 19:29.
I recently picked up a surplus battery-powered motor assist for a bicycle, and it's a lot of fun. Due to lower power you have to start peddling to 3mph and then it can run the bike for 10 miles at 10mph (for normal weight people, not me.)
All-electric cars didn't do well in the market in part because people were scared of their limited range, slow charging and and high cost, and the annoyance of plugging them in. They love hybrids because they don't have the range problem. Some folks are promoting plug-in hybrids, which are hybrids with lots of batteries. You can and should charge them from the grid, but you don't have to, so your range is the same as a gas car (or better) and on most trips you are much more efficient.
But perhaps cars are the wrong target. Electric bikes are heavy and a little more unstable when slow or being walked, and get really bad if you put enough batteries on them to go 20 or 30 miles. But trikes on the other hand are stable and you can load a lot more batteries onto them for serious range. And electric trikes are wicked efficient, in terms of cost (and fuel burned) per mile of travel. Orders of magnitude ahead of hybrid cars.
And all this is quite cheap to make if done in quantity. If our cities made more bike paths and bike lanes these trikes could become a major commute form, especially in California with its assured good weather. Yes, it's not perfect -- you have to recycle the batteries, and you do have rain to worry about, and the speed is definitely lower. But for shopping trips, neighbourhood trips and short commutes it seems a giant win.
Submitted by brad on Mon, 2005-08-01 12:06.
Mapping programs, and fancy GPSs come with map databases that will, among other things, plot routes for you and estimate the time to travel them. That’s great, but they are often wrong in a number of ways. Sometimes the streets are wrong (missing, really just a trail, etc.) and they just do a rough estimation of travel time.
Yet all the information is there, being collected constantly by every car that drives the roads with a GPS. Aggregating this data will tell you what roads are real, what roads might be missing, which are one-way, where freeway entrances and exists really are.
And it will also tell you real-world speed examples at various times and dates, at rush hour or otherwise. Even a range of speeds so you can know the speeds for faster and slower drivers and get a really good estimate of your own likely speed on a given road at a given time. After removing the anomalies (like people stopping for coffee) of course.
Rental cars with GPSs are collecting this all the time (sometimes to nefarious uses, like charging whopping fees for brief trips out of state). Technically this data can be had.
But here’s the bad part — there is a potential for giant privacy troubles unless this is done very well, and some may be impossible to do without a privacy risk. After all, until you upload the data, there is clearly a log of your travels sitting there to be used against you. Only a system with rapid upload (and which discards data that gets old, even if it’s not uploaded) would not create a large risk of something coming back to haunt you.
The data would have to be anonymized, of course, and that’s harder than it sounds. After all, your GPS logs say a lot about you even without your name. Most would identify where you live, though that can be mitigated by breaking them up into anonymized fragments to a degree. Likewise they’ll identify where you work or shop or who you visit, all of which could be traced back to you.
So here’s the Solve This aspect of this problem. Getting good data would be really handy. So how do we do it without creating a surveillance nightmare?
Submitted by brad on Wed, 2005-07-27 15:47.
Ok, this idea will make no sense to those who have not gone RV camping. RVs have 3 water tanks — one for fresh water, one for the toilet sewage (known as “black water”) and one for the other drains (shower, sinks) known as “grey water.” When you camp in unserviced campsites for a while you become very aware of the capacities of your tanks.
However, the RV uses the fresh water tank to “flush” the toilet. It seems to me that with a small extra water pump, one could use the grey water, or a mixture — grey with a final spurt of fresh to rinse the bowl.
RVs don’t really flush the toilet, that would use way too much water. You rinse the bowl after #1 and you pre-fill the bowl before #2 and rinse later. read more »
Submitted by brad on Wed, 2005-07-13 12:00.
Having completed a long fly-n-drive road trip, I have some lessons and observations.
If you will be driving a lot, use a rental car even if leaving your own city. We put 3000 miles on our rental car for $300 — far less than the depreciation cost would have been on my own car.
It’s great to have a cooler in the car, you can buy perishables and get cold drinks when you want them, but forget about those $5 styrofoam coolers for any long trip. Within a few days ours was leaking, we fixed it by putting a plastic bag inside and out, but they are not very sturdy. There are collapsible coolers and we have one but didn’t have luggage room. You can buy a cheap solid cooler for under $20 at wal-mart or Costco, but it seems wasteful to throw it away. If you have extra luggage, you can fill a cooler with stuff, duct tape it and check it as luggage, however. read more »
Submitted by brad on Sun, 2005-06-26 20:14.
This special forum topic exists to help people identify the best local company to use for a temporary prepaid GSM SIM card when you visit that country. If you research this, put your results here. In particular look for the best results for a short term visitor, who thus won’t care much about when the minutes expire and may or may not care when the number expires. A typical cost to compare would be the cost of the card and say 60 to 100 anytime minutes. However, if there is a major difference for somebody planning mostly night/weekend calling, note that.
Here are things to note in your comment:
- Company and their URL
- Price for SIM, price for a cost-effective prepaid card
- Ease of getting the card
- Other companies to check if this one isn’t convenient
- When will cheapest minutes expire, and how long after that does number expire
- Can you refill from overseas (ie. with non-local credit card)
- For comparison, cost of a prepaid account including (probably subsidy locked) phone. This bundle can be cheaper than an unlock and a naked SIM.
Important note: If you have any affiliation with a company you talk about or link to you must disclose it. No affiliate links allowed Furthermore, you must post your prices. (Create an account so you can come back and edit your posting when they change) and they must be one of the best deals out there. We want real information on the best deals, not self-promotion or typical vastly overpriced cards.
Submitted by brad on Fri, 2005-06-10 14:59.
Here’s an entry in my new “solve this” cateogry, which asks for reader input on solving problems.
When flying on a very full flight yesterday, we had an example of what my approach for faster airplane loading would have helped with. But until we get that, are there other solutions?
On the full flight, passengers would stand in the aisle trying to store their bags. With the compartments full they took a long time doing it, sometimes found themselves unable to. This blocked the loading and even though we started boarding 30 minutes before the flight, we were not finished by departure time. The flight attendants were on the PA every few minutes telling people not to stand in the aisle, to instead step into the row and let people pass, but very few paid attention to it. We don’t seem inclined to do this, and not just because we are desperate for storage space. (I’m one of the desperate, I carry on fragiles like camera gear that I refuse to let them throw around.) We just don’t believe that our own efforts will slow things much, and we also believe it will take “just a few more seconds” to get the bag in right.
… read more »
Submitted by brad on Tue, 2005-06-07 11:25.
So if you travel to different countries, you know that cellular roaming can be a pain, even with a GSM world phone, because they ding you for very high roaming charges.
So here’s a service I want. A kiosk in the airport to sell, or ideally rent me a GSM SIM card for a prepaid account, right in the airport. The kiosk would also sell me unlocking service for my phone, and of course prepaid cards. (By renting the SIM card, I mean it would sell it, and then buy it back at a reduced price on the way back out.)
Update Note: I’ve created a Special Forum to share information on the best SIM card sources in different countries. Search there for info on each country or enter your own findngs.
… read more »
Submitted by brad on Mon, 2005-04-04 14:38.
Perhaps this is one of those ideas that some car has implemented and I haven't yet seen it. As many people know, in several years ago a number of cars arranged so that their interior lights would not go off immediately when you closed up the car. This gives you the ability to still see shortly after closing up the car and walking away.
Of course this also drives people nuts, because in many cases you can't tell if the lights stayed on because you didn't close a door properly, and you would end up waiting around to see if they would go off.
Some cars fixed this by having the light fade out, but that's still pretty slow and of course elminates the light you were hoping for.
I would suggest that cars develop some more overt signal, to be triggered immediately when the car has decided that all doors are closed and the car is off, and the lights will be going off in 20 seconds. Such as a quick blink pattern when you close the door, or a flash of the headlights, or a quiet sound or bright internal LED.
Seeing this blink pattern, you would be 100% confident the car is closed and you haven't left the lights on, and could walk away, lit for a few seconds like you want.
Submitted by brad on Thu, 2005-03-10 18:36.
Update: Well, clearly this was already being done when I asked for it, just not at the airports I flew from. It's now close to universal.
Airport pickup is becoming another nightmare in some cities, with police barring cars from waiting for passengers, causing people to circle.
Airports should take a piece of parking lot and turn it into a marshalling area for people with cell phones. If you are picking somebody up, and you have a cell phone, you go to the marshalling area, where cars wait in parked lines like a parking lot. When you get a call from your passenger saying they have bags and are ready to go to the curb, then you go out and get into a special passenger pickup lane. You go right to the numbered spot your passenger told you. For passengers without cell phones, phone booths will sit at the exits of course.
For those not with cell phones, there is of course short term parking or the endless circling, though generally you want less of that.
Submitted by brad on Sun, 2005-01-02 12:08.
Just back from the nightmare of holiday travel, which started at 5:30am on Christmas morning and a security line snaking all the way to baggage claim. Coming back 6 days later, I braved the door to door shuttles from the airport.
I generally regret the decision to use these shuttles, which seem to average about 1 hour 30 minutes for the 35 minute drive to my home from SFO. This time, they had 10 people waiting for my town (which would normally be a dream as you would not spend all that time wanding around closer towns dropping off earlier folks) but in fact after we saw others had waited an hour for any shuttle to show up, we went to the caltrain, which takes an hour for the trip but is predictable.
The curse of these shuttles is how unpredictable they are. For some they are a quick trip but often they will drive you many times around the airport waiting for passengers, and then on an unpredictable drive. The public hates unpredictability even more than slowness, and would pay for predictability, I think.
So can computers, and some common sense, fix this? Surely you could make reservations which tie your flight number into the database so the shuttle company sees your plane arrive and knows pretty accurately when you will make the curb. (You can confirm that with a cell phone speed dial if your cell number is registered.) If lots of people did this, you could know how quickly a large enough group of people who live close together would be ready to leave. read more »
Submitted by brad on Sat, 2004-10-16 13:36.
I've written about a few plans to get rid of the headache (and travel killer) that airport security has become. One of the great curses is that because you can't predict how long security might take, most people end up arriving way, way ahead of their flight in case the line is long, but often they clear it in just a few minutes. (Ditto the immigration/customs line at Canadian airports going to the USA.)
So here's another idea -- appointments for going through airport security. When you use web check-in (which many airlines now support) or even at the gate, you would be allocated an appointment in the latest available slot some period (say 20 minutes) before boarding ends for your flight. Appointments would be spaced at slightly more than the average time to clear a passenger through security.
This would work because there would be two lines at the security gate. One for people with appointments, one for those without (or who missed their appointment.) You could only enter the appointment waiting zone in the 10 minutes prior to your appointment, and presuming 30 seconds per party, that would mean it would hold about 20 people. An agent would check your bar-coded appointment slot in letting you in.
When your time comes (or at any free time) you would be taken through at the head of the security line. If somebody needs extra security (random search, suspect item) that of course delays the station they are going through, but the other stations are free to take the person with the next appointment. Only if all stations got bogged down with problem cases would people in the appointment line not go through at close to their exact appointment time. read more »