Mike on Traffic

Safe Multi-modal Traffic at Schools

In 1969, about 40% of American elementary school children walked or biked to school.  In 2001, we dropped down to about 15%.  This is due to a shift in students living more than half a mile away from their school.  Not surprisingly, kids getting dropped off in private vehicles went from 15% to 50% over that same time period.  (Source:  NHTS Data Series)

I just tuned into a webinar by the Institute of Transportation Engineers' on designing safer school site's that work for all modes of traffic (personal cars, bikes, walking, school buses, and public transit).  Here's a summary of things to consider when developing a school site design:

Picking a Good School Site for Traffic Operations

1. Situate the sight within the neighborhood being served so more kids are within half a mile of the school (half a mile is the limit of a comfortable walking distance).  Ideally in the middle of the school boundary so kids are walking from all directions.
2. Avoid access from an arterial roadway or other roads with high traffic volumes.
3. Seek multiple street fronts so the site can have driveways on two local streets or collectors.
4. Locate the driveways so any potential vehicle backups will occur on low volume, local streets.
5. Provide bike and pedestrian connections on each side of the site.

School Site Traffic Operations

1. Minimize the number of points where kids mix with cars/buses.  Avoid pedestrian routes through parking lots and across driveways.
   
2. Provide separate areas for buses and carpool pick-up/drop-offs. 
3. Provide one-way, counterclockwise traffic patterns so kids are loaded/unloaded from buses or cars right onto sidewalks.
4. Locate the bus exit within the site upstream of the automobiles so the buses have priority in getting out of the site.  This will reduce overall delay.

Traffic Engineering Fundamentals Workshop

I'll be presenting at the Traffic Engineering Fundamentals Workshop on February 10th in St. Paul, MN (registration flyer).  The workshop is a great introduction to traffic engineering for entry level traffic engineers, technicians, city engineers, planners, etc.  It is also a great value - $75 ($50 if you're a member of NCITE) for a full day of continuing education with lunch.

The workshop has been presented annually for about 25 years now and continues to draw a good crowd.  It is sponsored by the Minnesota Local Technical Assistance Program and the North Central Section of the Institute of Transportation Engineers. Here are the topics that will be covered this year:

• Traffic Engineering:  Tips of the Trade
• Traffic Signal Operation Basics
• Encouraging and Measuring Pedestrian Traffic
• Travel Demand Management (presented by yours truly)
• Highway Safety Update

I hope to see you there!

Roadway Safety Improvements – Curve Warning Signs

The Federal Highway Administration has decided to study a host of low cost safety devices to determine whether they do in fact work.  Surprisingly, the effectiveness of many types of warning signs has never been studied.  The effectiveness of providing more conspicuous signing and lane markings at roadway curves was recently analyzed in FHWA Publication Number FHWA-HRT-09-046.  

Crash data for horizontal curves on rural, two lane roads was collected in Connecticut and Washington.  Connecticut has recently been upgrading their existing curve warning signs to fluorescent yellow sheeting as well as adding fluorescent yellow curve warning signs to locations that previously had no curve warning signs.  Washington has recently focused on installing more chevron curve delineation signs (type W1-8), either adding chevrons to previously unsigned curves or adding more chevrons to previously signed curves.  Crash data was collected on roadways with the improved curve warning signs and compared with crash data from similar roadways where the improved curve warning signs had not yet been installed. 

The most significant safety improvements were related to crash reductions during dark conditions and the reduction of injury plus fatal crashes.  Crashes on curves during dark conditions were reduced by 35.3% in Connecticut and 24.5% in Washington.  Injury plus fatal crashes were reduced by 25.2% in Connecticut and 18.0% in Washington.  These findings were found to be significant at the 95-percent confidence level, meaning there is a strong correlation in the statistical data between installing curve warning signs and reducing these types of crashes. 

An economic analysis was also done on improving curve delineations with warning signs.  It was found that installing curve warning signs on rural, two lane roads is very cost effective with a benefit-cost ratio exceeding 8:1.  A ratio of 2:1 or better is typically considered a good investment.  In short, improving curve warning signs is a very good idea.

Help - people are speeding in my neighborhood and I need a stop sign!

I've had two calls this fall from private citizens wanting me to help them convince their city engineers to install stop signs in their neighborhoods.  Up until a month ago, I thought I left this topic behind when I left Maple Grove.  Here is the gist of how I responded to the request.

All way stop signs only work when there is heavy enough traffic at the intersection so people need to stop (the rules are below from the MN Manual on Uniform Traffic Control Devices).  Otherwise your neighbors get conditioned that there is no crossing traffic and they start blowing the stop signs because there isn’t a reason to stop.  This phenomenon is well documented (the same way people drive 65 mph on most highways unless a police officer is present, then everyone magically goes 55).  I personally studied this in Maple Grove when I was on the staff there.  We found about 20% of people didn’t even touch the brakes for the stop sign.  This is very dangerous for everyone who goes through the intersection.

The only way to control speeds is with traffic calming measures, which are well documented here - http://trafficcalming.org/.  I can do a full study on the intersection and come up with a recommended solution, if there is a problem (as defined by high traffic volumes, high speeds, or high numbers of crashes).  The city engineer will probably collect the traffic volumes and come back saying you do or do not meet the criteria below.

 

p.s.  I like the leaves someone put on the stop sign post.

Travel Demand Management - Does it work?

Travel Demand Management (jargon alert - TDM) strategies are simply ways to encourage people to stop driving to work by themselves during rush hour.  Do they work?  I don't know.  They sound good (promote bike riding, promote transit riding, give people money if they carpool, charge for parking, etc. should get people to not drive by themselves).

We're midway through the Apprentice program and our group has decided to tackle this question.  We started with a literture search.  TDM has been around in the U.S. since the oil crisis of the 1970's, so you'd think there would be a lot of study done on the subject.  There are some good resources out their explaining what TDM is and how to implement it.  There are also a few case studies that describe wildly successfful TDM plans.  But we couldn't find a systematic study that even hinted that TDM might not work.

We're in the middle of the data collection phase of our project.  We're collecting data from office buildings that have active TDM strategies (both data on the strategies and actual cars coming in and out of their parking lots).  Then we'll calculate trip generation and parking generation rates for the buildings.  The proof will be in the numbers.  Do the office buildings with TDM strategieswe're studying in fact generate less traffic and parking demand when compared to "normal" office buildings (we'll compare them with the Institute of Transportation Engineers' rates)?

In the dream world, I hope to put this out as an open source project so folks around the country can collect data at more sites.  With a database from hundreds of sites, we could hone in on the effectiveness of specific strategies and also identify best practices that could be implemented through our industry.  

Stay tuned. 

Using dashed striping to control speeds?

We recently finished reading Traffic by Tom Vanderbilt in my apprentice program.  It is my second time through the book and I think it is a must read for anyone dealing with traffic.  Tom does a good job of translating research so we can all understand it.  He deals mostly with the psychological aspects of driving, which us traffic engineers don't really study in college.

One of the book's takeaways for us traffic engineers is that people drive as fast as the environment tells them to.  I've personally seen this in my neighborhood.  I live in an eighty year old neighborhood on a grid system.  We have mature trees building a canopy over the road and we have sidewalks.  We also have a fair amount of cars parked on the street.  The natural speeds in my neighborhood are about 5 mph less than the speeds in Maple Grove where I was the city traffic engineer for a few years.  Amazingly, the residential streets in Maple Grove are slightly narrower than in my St. Louis Park neighborhood.  But they don't have sidewalks, trees, parked cars, etc.

So here is a crazy idea on how traffic engineers can subtly affect the roadway environment (I haven't found research on this specific idea, but I'd love to read about it if you have seen any test cases) - we should alter the skips on the pavement based on the speed limit.  The standard (no matter what the speed limit is) is for a 10 foot long white or yellow line, a 40 foot blank space, and then another 10 foot line.  Let's leave that on the 65 mph roads, but lets make the line shorter and have shorter gaps as the speed limit is reduced.  A human factors lab should do simulations to determine the correct length/gap ratios so we always "feel" like it is the same when we are going the speed limit - whether the speed limit is 30, 40, 55, or 70 mph.  The skip could be a subtle indicator to help our brains figure out the appropriate speed for the road.  If you are going too fast on a road with this new speed limit based configuration, it would start to seem like you are doing a Star Wars hyperdrive in the Millennium Falcon because the skips would be gong by "too fast."

Warning Signs - More Effective Alternatives?

When was the last time you saw a child playing next to a Children at Play sign, rocks falling by a Falling Rocks sign, deer crossing by a Deer X-ing sign...   Didn't we all learn the perils of "crying wolf" in kindergarten?  Because the warning signs warn of phantom dangers, our brains learn to tune them out.  Tom Vanderbilt details the research on this phenomenon very well in his book Traffic.

So what should we do along those rural county roads that have a high proportion of deer/car collisions?  I'd like to see a test done where we make up a semi-realistic looking stuffed deer - probably made out of canvas, filled with a lightweight material so it weighs about fifty pounds, with some red paint on it.  We have the county public works guys move this around the "dangerous" corridor every few days when they are making their normal rounds.  This would provide a real, semi-dynamic warning to motorists that they are on a corridor that has a lot of deer crossings.  Or we could train the deer to cross at the yellow crossing signs (apparently under bridges so they won't get wet when it rains).

Landscape Medians Enhance Traffic Safety

Thanks to Rick Perez, PE for pointing out this interesting research on landscaped medians.  Originally, the Washington DOT was concerned about the negative safety implications of planting trees in boulevards - they obstruct sight lines.  A summary of the before/after results from the report's abstract:

    Total, fatal, fixed object, pedestrian/bicycle, tree, curb/median and U-turn accident rates were analyzed. The percentages of intersection-related, driveway-related, and other accidents were analyzed. Overall, accidents decreased significantly for the treatment locations, but no other types of accidents showed significant changes at either the treatment or the control locations, except for the percentage of other types of accidents at the control locations, which increased significantly.
    It appears that the installation of landscaped medians does not have a detrimental effect on safety and may result in an overall decrease in accidents, conclusions consistent with those of the first phase.

Without boldly saying it - the research says crashes decrease on arterials with landscaped medians.  I don't think this is surprising since the before conditions and control conditions had no medians (they either had two way left turn lanes or no median/center turn lane).  It is noteworthy that the trees didn't seem to cause problems.  As usual, we could use more research to confirm the results but this is quite encouraging for us who believe in Context Sensitive Design.

Traffic Presentations at Public Hearings

Traffic is often a scapegoat used by neighbors at public hearings (in front of county boards, city councils, planning commissions, etc.) to try to kill a proposed development project.  It is a favorite tactic used by those opposed to new Walmart stores (at least the dozen or so public hearings I have attended for my Walmart traffic studies). 

I attended an emotional public hearing with a developer for his proposed strip mall/gas station development a few weeks ago where traffic issues were raised.  Through a lot of practice, I have honed my presentation skills so I am ready to speak up for my clients at public hearings.  Two big lessons - tell stories to make the statistics easier to digest and know when to stop talking.

Brief tangent, but I promise to circle back -

I just finished reading Made to Stick, which I highly recommend.  At the beginning of Chapter 5, Dan and Chip Heath talk about research done that proves people will donate more to a single person than to an entire cause.  The researchers at Carnegie Mellon set up a donation letter asking people to donate to Save the Children, a charity that helps kids in Africa.  A second letter described a little girl in Africa named Rokia and then asked for donations for Rokia.  The average donations for the Rokia letter were more than double that of the Save the Children letter. 

The Carnegie Mellon researchers did a subset analysis with the Rokia letter.  They asked half of a group, "If an object travels at five feet per minute, then by your calculations how many feet will it travel in 360 seconds?"  The other half of the group was asked, "Please write down one word to describe how you feel when you hear the word 'baby'."  Then they gave everyone in the group the Rokia letter and asked for donations.  The "baby" group gave about the same amount as the previous Rokia letter donators.  Those who did the math gave about half the amount of the previous Rokia letter donators.

Here is the conclusion from the Heath's, "These results are shocking.  The mere act of calculation reduced people's charity.  Once we put on our analytical hat, we react to emotional appeals differently.  We hinder our ability to feel."

TAKEAWAY - emotion is the enemy of a traffic engineer making a presentation at a public hearing.  Under most scenarios, we want the city council to make a logicial decision based on our work.  So, traffic engineers (and developers?) should warm up at a public hearing with some subtle calculations to diffuse the emotions in the room.

Gridlock Buster from U of MN

Ever wanted to try your hand at traffic signal timing?  Here's your chance - the University of Minnesota has developed the "Gridlock Buster" traffic control game.  The University is trying to entice young folks into giving civil engineering a try.  Read more here.

I played a few levels (don't tell my boss).  Fun, but not addictive.