One thing that is constantly bounced around is why tour-based modeling is better than trip based modeling.  We’ve been using trip based modeling for 50 years, isn’t it timeless?

No.

Fifty years ago, when the trip based modeling methodologies were developed, the primary reason was to evaluate highway improvements.  While tolling was in use, the bonding requirements were likely different.  Transit, while extremely important, was not in the public realm (the streetcars were normally privately owned by the area’s electric company).

Now, there are a lot of demands on travel models:

• Tolling/Toll Road analysis at a better level
• Different tolling schemes (area tolling, cordon tolling)
• Travel Demand Management (telecommuting, flex hours, flex time, alternative schedules)
• Better freight modeling (which now is becoming commodity flow and commercial vehicle modeling)
• Varying levels of transit (local bus, express bus, intercity bus, BRT, light rail, and commuter rail

While many of these can be done with trip based models, most of them cannot be done well with trip based models.  There are a number of reasons, but the few that come to mind are aggregation bias, modal inconsistency, and household interrelationships.

Aggregation Bias

Aggregation bias occurs when averages are used to determine an outcome.  For example, using a zonal average vehicles per household, you miss the components that form the average, such as:

20 households, average VPHH = 2.2
2 HH VPHH = 0
5 HH VPHH = 1
4 HH VPHH = 2
6 HH VPHH = 3
3 HH VPHH = 4+

The trip generation and modal choices (car, bus, bike, walk, etc.) among these households are all different, and are even more more different if you look at the number of workers per household.

Modal Inconsistency

In trip based modeling, “people” are not tracked throughout their day.  So, if someone rides the bus to work, there is nothing in the model to ensure that they don’t drive from work to get lunch.  While we don’t want to force people to use the same mode, since many people will use the bus to get to work and then walk to lunch or to go shopping during lunch, we want to make sure that there is some compatibility of modes.

Household Interrelationships

One of the features of of tour based models is determining each person’s daily activity pattern.  During this process, certain person types can determine what another person is doing.  For example, if a preschool age child is staying home, an adult (whether they are a worker or not) HAS to stay home.  Another example is if a school-non-driving-age child is going on a non-mandatory trip, an adult must accompany them.  Trip based models don’t know about the household makeup and the household interaction.

The above are only three of the many reasons why tour-based modeling is important.  There are many more, but I feel these are some of the most important and some of the easiest to understand.

I am going to concentrate this blog on transportation starting now.  The old stuff is going to be moved to another location on the server… I think… I have to figure that out.  Moving forward, though, transportation and transportation technology.

The short answer: they are.

The long answer (and previously blogged): the study was a before and after study that claimed that cell phone laws have no effect.  Such is the case when you don’t and can’t enforce it.  Cell phone bans are difficult to enforce (as are speed limits).  Most police departments have their hands full as it is, and their budgets are being affected (negatively) by the economy.  The original study was basically a before and after study of the same conditions on both sides.

Why Cell Phones and Driving Aren’t Dangerous | Psychology Today.

In what is perhaps an accidental approach to reducing pedestrian crashes using the first step of “the three Es” (education, enforcement, engineering), Pecica, Romania has installed signs that warn of drunk pedestrians ahead.

While a little odd, I applaud the mayor for experimenting with a low-cost, low-impact way to handle the problem.  I hope it works.

Romanian street sign warns drivers of ‘drunk pedestrians’ – Telegraph.

As my close friends and colleagues know, I shunned my AICP certification almost a year ago.  The reason was based on a few things:

• For the $400 I would have spend on APA+AICP, I can have ITE+TRB, which are more vital to any transportation planner
• I really don’t want to be a member of APA.  It has done little for me, and Planning magazine has published questionable articles on more than one occasion.  One article even made me think that the author was high on drugs.  However, you cannot split APA and AICP.
• While the AICP Commission tried to make AICP actually mean something by requiring CM, their one step forward took two steps back when they attempted to use it as a money-making opportunity for APA and requires approval for all hours.  This means that if you go to Ohio Model User Group meetings or attend Travel Model Improvement Program webinars, you’re not getting any certification maintenance credit for it.  If you are a Professional Engineer or a Professional Transportation Planner (the certification through TCSB), you get credit for these things.

In keeping up with things going on in the field, I received an email from the Florida DOT Weekly Briefs.  In it, they had a link to “State of Transportation Planning 2010″.  They had an overview of some important topics (with suggested reading), but missed two, including:

• FINANCE. one of the biggest topics currently impacting transportation.
• SAFETY.  There are almost 40,000 people killed on America’s roads and another 300,000 injured.  Distracted driving has received a lot of attention because of the crashes that it causes and has the potential to cause.  Toyota has recalled some 8 million vehicles due to problems with sticking gas pedals, brakes, or steering.

Aside from the obvious blunders above, there are a few more that I think need to be pointed out.

First off, this is not a “state of” anything.  This is a very basic introductory document that points people to a few seemingly randomly selected works in that field.  Looking at the travel behavior section, there are several research works (and having met some of these authors, I know they are great resources).  The one thing that we already have as travel demand modelers that illustrates the “state of” is Transportation Research Board Special Report 288.  It is so vitally important to us that we know it by number (and it is the only one, in my case).  SR288 goes through in sometimes painful detail to talk about the state of travel forecasting.

Second off, policy is centered entirely around climate change.  They evidently haven’t been following Climategate, else they would have dropped the link to “Moving Cooler” (considering that areas near Washington DC received an uncharacteristic 5 feet of snow in some places, you’d think that might tip them off).  Obviously, the jury is still out on whether the globe is getting hotter or colder, but if you talk with real people, many feel that Global Warming isn’t occurring.  Stuff like that happens when you mess with data and hard code models for certain outputs.

So yeah, as Marty Brenaman (play-by-play radio host for the Cincinnati Reds) says quite often, “A swing and a miss”.

Here’s the link: TPD_State_of_Transportation.

In response to a blogger at Entrepreneurs: Start. This. Company. Now. – washingtonpost.com.

I have always shied away from anything Tech Crunch, since it has been one of the most likely sites to report hoaxes and rumors.  The above link was posted to PlaNetizen and went out to thousands of readers.  I’m sure there are hundreds saying “Get your head out of your ass!  We have that here!”

Those hundreds are in Tampa.  They have an elevated freeway above the Lee Roy Selmon Cross Town Expressway.  They were finished in 2007 or so.  I’ve heard that they are really, really cool to use.  It was also really, really expensive, and it suffered a setback after one of the support piers sunk, bringing a 3 lane section down to the ground level freeway below.

Another thing that should be pointed out is that in this country there are dozens of bridges that are double-decker.  We have one here in Cincinnati, the Brent Spence Bridge, which carries I-71 and I-75 over the Ohio River.

That bridge needs to be rebuilt.  It is roughly a half of a mile (including the approaches), and the costs are measured in the billions.

Dear author, if you are going to tell people to start a company, make sure it hasn’t already been started first.

EDITS:

(1) I figured I needed to come back to this and bring up an important issue that I only touched on.  That is the potential for problems caused by natural disasters.  After one of the “Big Ones” in California, it was brought up that Cincinnati is somewhat earthquake-prone.  The thing that made the nightly news?  ”Is the Brent Spence Bridge Going to Collapse if Cincinnati gets hit with a Big One?”  Certainly the Tampa Crosstown Expressway sink was a scary, serious issue.  It was one that was not planned for, and required a complete redesign of an area of the elevated expressway.  The reason roads tend to be on the ground is because there is a limited set of catastrophic natural disasters that can happen.

(2) I dogged TechCrunch above, and I figured I should mention that despite my general poor opinion, I did read another article that sourced a number of topics to TechCrunch, and the source data sounds spot-on.  I’m not a TechCrunch reader, and my opinions are still mixed.

Reference: National Journal Online — Insider Interviews — Bush DOT Chief Discusses Reauthorization.

I agree with the thoughts of increased tolling and more fees other than the gas tax.  I also agree with $1B per year for technology, but it has to be managed right.

I’m also glad that the performance measures are measurable:

• Congestion (we can measure that – it is the percent of a region’s network that is operating with a demand greater than its capacity)
• Costs (we can measure that, although we have to watch how we do it, as we don’t want to have a system be considered bad if gas prices hit $4/gallon)
• Safety (we DO measure this – it is the number of injuries and deaths on the road)

It is the start of traffic counting season in Ohio. Each year, we get about 7 months to count the cars on the road. With my involvement in this type of work, I hear a lot of horror stories. First off, I wanted to discuss how these things work and how the data is used and cannot be used, and then show some of the war stories.

Traffic Counter on side of road

First off: how these things work

Those that have been around for 30 or more years may remember when some gas stations had a hose that rang a bell to call a station attendant to pump your fuel. Those that don’t should watch Back to the Future. This is the same basic concept for most traffic counters. There are hoses that go across the road, and based on what the sensors feel and the time between them, these little green (or sometimes gray) boxes calculate the number of axles, distance between them (which can be used to derive the type of vehicle), and the speed.

I know that speed is a big issue with a lot of people. After all, some of these counters are being used for speed studies to see if they want to put a cop on a road at a certain time. This does happen, despite my wishes that cops and others would use less-detectable methods for enforcement. There are two other ways that counts, with speed, can be taken. One is by RADAR (the same thing they use for active speed enforcement). Mind you, for speed sampling, RADAR is pretty useful when installed correctly, and the boxes can be hidden quite well. The other is using magnetic loops. There are portable models of these that sit in the lane and are difficult to see (and also susceptible to theft). There are also permanent models that can be completely hidden from view.

One thing I can say with ALL hose counters: WE CANNOT USE THEM FOR SPEED ENFORCEMENT! The units do not have any cameras (etc), so if you speed while going over them, we know you did, but we don’t know who you are!

Second off: How We Use The Data We Get From These Things

This one differs by jurisdiction, but most use it for traffic studies. Speed, count, and vehicle type are very useful for roadway improvement design. Another use is for travel model validation. We (specifically me, since it is my job) use this to ensure that the region’s travel model is accurate so when we use it to plan billions of dollars in improvements, we know we’re not just guessing, which would be a waste of money.

Law enforcement will use the number of speeders per unit of time to plan when to run patrols. As I indicated, I wish they wouldn’t use hose counters for this, but they do, and the data they get is accurate. However, hoses are pretty conspicuous, which is why I wish they wouldn’t use them.

We cannot use the data in court. You cannot be detected to be going 45 MPH in a 25 MPH zone based on a traffic counter. The counters do not have cameras in them, and none that I know of can connect to a camera. A camera would be required to prove who was speeding. Without the connection, it would be difficult to prove, since the times would have to be the same, the counter has to be operating perfectly, and the hoses have to be measured very precisely. Some states also forbid the use of cameras for passive law enforcement (a cop can actively use a RADAR+camera, but not mount one on a pole and get every car that is speeding).

The War Stories

I have two, both given to me by a salesperson for Jamar Tech, one of the leading traffic counter manufacturers.

City of Boston Thinks a Counter is a Bomb. This one is proof that some cops don’t use hose counters, else they would have known what this unit is.

Counter burned, likely by an accelerant. PDF from Jamar, which the salesperson sent me just after I bought 8 counters from him.

Don’t Mess With Them!

It amazes me that 1 month into the season, I’ve had to replace several hoses because of cut or stolen hoses. This is your tax dollars at work. The more hoses we have to replace, the less money we have to improve the roads.

It occurred to me that many people likely do not understand all of the terminology of travel demand models.  Because of this, I felt the need to list many of them here. Read the rest of this post… »

I’ve occasionally seen some road nicknames that are particularly good.  A few that I’ve heard:

• Malfunction Junction (I-275 and I-4, Tampa, FL)
• The Riddle in the Middle (Alaska Way, Seattle, WA)
• Spaghetti Junction (I-85 and I-285, Atlanta, GA)

I’ve also started calling a strech of Columbia Parkway (Cincinnati, OH) “The Suicide Side”, which is a 45 MPH arterial that everyone goes 60 MPH.  The divider is a double-yellow line… only.

Got any more?  Add ‘em in the comments.

Trip generation is likely one of the easiest parts of the four step process.  Normally, the most difficult part of dealing with trip generation is getting the input socioeconomic (population and employment) data correct.  This post explains how trip generation is calculated in the model… Read the rest of this post… »

The center of most travel demand models is the “Four Step Model”.  This model was created in the 1950s to determine the demand on roadways.  The four steps include:

1. Trip Generation
2. Trip Distribution
3. Mode Choice
4. Trip Assignment

Read the rest of this post… »