Mike on Traffic

Copying Free Aerial Photos Into Reports

Lots of companies have free aerials out on the internet - google, microsoft, ask, yahoo....  Ask.com (then click on city) seems to have the crispest aerials for a wide area (go to ask.com and click on city).  Anyone who needs to put together reports about physical locations (engineers, planners, real estate appraisers, lawyers....) should have maps in their reports so people can get oriented.  I fall in this camp with my traffic studies.  Many state and county property record websites also have great aerials, but it takes more digging.  Here is the procedure I go through:

1. Go to your aerial site (I recommend ask.com and click on city).
2. Zoom into the area you want.
3. Press the key combination Alt + Prt Scr.  This captures a screen shot of the aerial.
4. Go to paint, MS Word, etc. and paste in the aerial (right click on your mouse and paste, among many other ways to paste).
5. Crop off the border of the screen that you don't want.

Mn/DOT's Intersection Control Evaluation (ICE) Report

The Minnesota Department of Transportation (aka Mn/DOT) put together a procedure last year for determining the correct traffic control to be placed at their intersections, which the nicknamed "ICE."  They put out a technical memorandum detailing what they are looking for, but it is pretty open ended.  Today I attended a class put on by John Albeck, who was hired by Mn/DOT to teach a class on the new procedure.  John did a good job of putting together a manual (which included once of my ICE Reports in the Appendix as an example!) and making a dry topic pretty interesting. 

The new ICE Report is supposed to look at everything from do nothing to build an interchange.  This includes changing access and implementing several "non-traditional" intersection types (like jughandles and Michigan Lefts).  I expect the vast majority of ICE Reports will thoroughly analyze: do nothing, all way stop sign control, roundabout control, and traffic signal control.   These are the standard intersection control options in Minnesota.  Other options will be analyzed in those rare instances where one of the four standard control options doesn't work well.

This procedure is going to replace the traditional Signal Justification Report procedure typically used.  Mn/DOT is only rolling this procedure out for intersections on their highways, but just about everyone at the class expects the procedure will trickle down to the county and city level.  The procedure is a good one.  It forces engineers to thoughtfully consider all of the options.

Mr. Traffic Engineer - What is Level of Service?

Traffic engineers grade the operation of an intersection as A, B, C, D, E, or F based on the amount of time each vehicle has to wait to go through the intersection during a particular hour.  We use grades to give non-engineers a feel for how the intersection operates.  We don't want to get hung up on fractions of seconds.  Every jurisdiction I know of considers Level of Service (aka LOS) A, B, and C to be acceptable.  Most jurisdictions in Minnesota considers LOS D to be acceptable, but LOS E and F are both unacceptable.  Some places, like Los Angeles, consider LOS F ok depending on how bad it is (the seconds of delay calculated).  You need to check with the jurisdictions who control the intersection.  I have been burned a few times by "unique" standards different jurisdictions have in their policies or ordinances.  Checking the local standards is now one of the first things I do on a new project.

For you technical types, the chart below shows the amount of Control Delay (in seconds) that makes up each category.  These are defined in the Transportation Research Board's 2000 Highway Capacity Manual.

                                       

Level of   Service	Intersection   with     Traffic Signal	Intersection   with     Stop Signs
A	≤10   sec	≤10   sec
B	10-20   sec	10-15   sec
C	20-35   sec	15-25   sec
D	35-55   sec	25-35   sec
E	55-80   sec	35-50   sec
F	>80   sec	≥50   sec

Note - the chart is different for traffic signals and stop signs.  This reflects people having more patience sitting at a traffic signal than a stop sign.  To date, there are no Level of Service standards for roundabouts.  Most traffic engineers fudge this by applying the delay table for stop signs to the amount of delay calculated by software programs such as VISSIM, Rodel, or Arcady.  It is not an apples to apples comparison.  Hopefully the next edition of the Highway Capacity Manual will address Level of Service at roundabouts.

I-35W Bridge Collapse - Traffic Management Lessons Learned

I attended an NCITE breakfast meeting yesterday where Jim Kranig from Mn/DOT and Don Sobania from the City of Minneapolis gave presentations on the traffic management response to the I-35W Bridge Collapse.  Here is my take on their presentations (these aren't bullet points from their slides).

Jim's Top 5 Comments:

1. Mn/DOT is very fortunate to have over 100 changeable message signs they can deploy around disasters to manage traffic.  They have a partnership with a radio station and were able to switch the radio station over to live coverage within ten minutes of the disaster.  This was put on the message signs, so motorists had a way of quickly becoming well informed.
2. They have over 150 cameras on the Twin Cities freeway system.  The RTMC was able to look at the collapse immediately and monitor the road network around the site.  They have been able to make minor changes to their system and then monitor their changes in real time.
3. Mn/DOT has FIRST trucks roving the system.  They were on site within 20 minutes putting up barricades.
4. Mn/DOT deals with crashes on the freeways on a daily basis and closes freeway segments several times a year for things like semi-trucks rolling over.  The bridge collapse was significantly more severe, but Mn/DOT's experience allowed them to respond quickly and appropriately.
5. The Twin Cities has a robust 800mhz communication system in place.  It worked amazingly well during the disaster.  All agencies were able to communicate with each other.  Minnesota took this lesson learned from 9/11 to heart.

Don's Top 5 Comments:

1. Don started with a few "funny" slides that showed how lacking Minneapolis is when it comes to the "tools" Mn/DOT has. 
2. Minneapolis doesn't have an emergency operation response center, but the traffic engineering conference room became their default center.
3. Minneapolis didn't have a comprehensive phone number list.  Luckily they were able to get the word out to their employees in a peicemeal fashion.
4. The local street network has to carry the 80,000 vehicles per day that used the bridge to access downtown Minneapolis.  Those people are finding creative ways to use the street system and the ripple effect is out further than they first thought it would be.
5. The disaster consumed upper management's time for a month.  Minneapolis didn't have an organizational system in place to shift decision making responsibilities if the head honchos were out.  Luckily, the city has great staff and was able to basically operate on cruise control.  In the future, they need to develop a better organizational structure to deal with emergencies.  There is still routine public works business that has to be done even if you just had a disaster two weeks ago.

What should the scope of a traffic study be (Part 2 of 2)?

See Part 1 for the intro on scoping a traffic study.  It dealt with how far away from the development the study area needs to address.  This post (Part 2) discusses how far into the future we need to analyze.

The Institute of Transportation Engineers (aka ITE) has developed a Recommended Practice titled Transportation Impact Analyses for Site Development ITE’s Recommended Practice. It details the study area limits that should be used for different size developments. The following list presents ITE's guidelines.  You can use this as a starting point to make sure your traffic study has the proper scope.

Small Development (less than 500 peak hour trips)

• Anticipated opening year, assuming full build-out and occupancy

Moderate Single Phase Development (500 – 1,000 peak hour trips)

•  Anticipated opening year, assuming full build-out and occupancy
• 5 years after opening date

Large Single Phase Development (more than 1,000 peak hour trips)

• Anticipated opening year, assuming full build-out and occupancy
• 5 years after full build-out and occupancy
• Adopted transportation plan horizon year, if the development is significantly larger than that included in the adopted plan or travel forecasts for the area

 Moderate or Large Multiple Phase Development

•  Anticipated opening years of each major phase, assuming full build-out and occupancy of each phase
• Anticipated year of complete build-out and occupancy
• Adopted transportation plan horizon year, if the development is significantly larger than that included in the adopted plan or travel forecasts for the area
• 5 years after opening date if completed by then and there is no significant increase (less than 15 percent) in trip generation from adopted plan or area transportation forecasts

What should the scope of a traffic study be (Part 1 of 2)?

This is a big question because the scope of the study will lead to the physical mitigation measures the developer will be responsible for. Scoping a traffic study is based on the size of the development and the type of location it is going into.  On a small development, the developer might be required to add a turn lane at the main driveway. For a regional shopping mall, the developer might be required to build a freeway interchange a mile away. If there aren’t feasible mitigation measures, the responsible government agency may require a less dense development or a phasing plan that is dependent on public infrastructure improvements.

There are two key components two the traffic study.  This post focuses on how far away from the development the study area needs to address.  A follow-up post (Part 2) will address how far into the future we need to analyze.

The Institute of Transportation Engineers (aka ITE) has developed a Recommended Practice titled Transportation Impact Analyses for Site Development ITE’s Recommended Practice.  It details the study area limits that should be used for different size developments. The following list presents ITE's guidelines.  You can use this as a starting point to make sure your traffic study has the proper scope.

• Fast Food Restaurant - Adjacent intersection if corner location
• Service Station (with or without fast food counter) - Adjacent intersection if corner location
• Mini-mart or convenience grocery with or without gas pumps - 660 feet from access drive
• Other development with fewer than 200 trips during any peak hour - 1,000 feet from access drive
• Shopping center less than 70,000 sq. ft. OR a development with 200 to 500 peak hour trips - All signalized intersections and access drives within 0.5 miles from a property line of the site and all major unsignalized intersections and access drives within 0.25 miles
• Shopping center between 70,000 sq. ft. and 100,000 sq. ft. OR an office or industrial park with 300 to 500 employees OR a well balanced, mixed use development with more than 500 peak hour trips - All signalized and major unsignalized intersections and freeway ramps within 1 mile of a property line of the site
• Shopping center with more than 100,000 sq. ft. OR an office or industrial park with more than 500 employees OR any other development with more than 500 peak hour trips - All signalized intersections and freeway ramps within 2 miles of a property line, and all major unsignalized access (streets and driveways)      within 1 mile of a property line of the site
• Transit Station - 0.5-mile radius

Is traffic generated by new development's killing kids in Minnesota?

What are all of these kids doing at a public hearing? It is already 9:30 p.m. It has to be past their bed time. “Dad” parades all of the kids up in front of the City Council during the public comment period. He asks the Mayor which one of the kids the Council would like to have killed by traffic coming out of the proposed residential sub-division. This really happened and different variations on this theme routinely happen as neighbors try to stop development.

As a consultant traffic engineer, I speak at a lot of public hearings to help developers address traffic related opposition. While most of the resistance to new development and re-development projects boil down to resistance to change, local residents claiming that traffic will get worse with the new development is a common objection. Public officials and developers should be armed with real data when confronted with this awkward situation.

First of all, I don't want you to think I take traffic safety lightly.  Fatal crashes on Minnesota's roadways are a significant problem. They are so serious that the Minnesota Department of Transportation, Minnesota Department of Public Safety, Minnesota State Patrol, Federal Highway Administration, and the Center for Transportation Studies at the University of Minnesota have banded together in a Towards Zero Death campaign. These organizations are cooperating to reduce the deaths on Minnesota roads through education, enforcement, and engineering measures.  

The good news is that road deaths around the nation are declining. The number of deaths on the nation’s roadways has dropped from 50,894 deaths in 1966 to 42,636 in 2004. This doesn’t look like a big change, but it is if we look at the statistics in terms of how many miles Americans are driving. According to the National Highway Traffic Safety Administration, the current fatality rate is 1.46 deaths per million vehicle miles traveled in the United States.  In 1966 there were 5.5 deaths per million vehicle miles traveled. The almost 4 fold decrease in the fatality rate is due to things such as improved roadway design, traffic control standardization, crumple zones in vehicles, seat belts, air bags, faster emergency response, drunk driving enforcement, and a host of other measures. These initiatives by the car manufacturers, transportation engineers, and enforcement agencies have had a large composite effect. This is great news, but this data still won’t calm down the parent who thinks their child is going to be killed by traffic from the next subdivision. We need to turn to fatal crash statistics within neighborhoods. 

Within neighborhoods, pedestrian crashes are rare and don’t follow a cause/effect pattern that can easily be identified or corrected. The National Highway Traffic Safety Administration published a technical report in 2003 titled Pedestrian Roadway Fatalities. The report found that of the 18,118 pedestrians killed by vehicles in the United States between 1998 and 2001, 2,580 (14%) of them occurred within urban neighborhoods.  The rest of the fatalities occurred on higher function roadways outside of residential neighborhoods. 

More encouraging is the National Highway Traffic Safety Administration’s Traffic Safety Facts (2003) report that found:

“In 1993, there were 768 pedestrian fatalities in the 0-14 year age group. From 1993 to 2003, the number of pedestrian fatalities in this age group decreased by 49 percent, with the 4-7 year age group showing the largest decrease.” 

Even though we are driving more and we are building more subdivisions, we are doing it in a safer manner. 

I sifted through Mn/DOT’s crash records to wrap my arms around Minnesota's pedestrian crash statistics. According to Mn/DOT’s crash data, there were approximately 275,000 vehicle crashes from 2002 to 2004. Of those 275,000 crashes, 3,772 (or 1.3%) involved pedestrians.  Of those 3,772 crashes involving pedestrians, 843 occurred on local urban streets resulting in: 2 fatalities, 813 injuries and 28 incidences of property damage with no apparent pedestrian injury. The remaining 2,929 pedestrian related crashes occurred on higher order streets. This data reinforces the small number of vehicle/pedestrian crashes that occur in neighborhoods.

 

Top Ten Developments Needing a Traffic Study

A lot of developers ask me if they need a traffic study for their specific development.  For starters - if a government agency says you need one, you'll need one. They aren't going to approve your project or your access without it.  A lot of jurisdictions have their own policies, so check with the jurisdiction you are working in first.  A general starting point though is the Institute of Transportation Engineers (aka ITE) recommendation of studying developments generating more than 100 trips during a peak hour.

(Jargon Alert! Traffic engineers define a vehicle coming in or out as a trip. So a car getting gas is two trips for the gas station - one trip entering and one trip exiting during the same rush hour.  At an office, you have most cars entering in the morning rush hour as one trip and exiting in the afternoon rush hour as the second trip.  Traffic engineers also like to call the morning rush hour the a.m. peak hour and the evening rush hour the p.m. peak hour.)

Top Ten Developments Triggering ITE's Thresholds

1. Fast Food Restaurant with a Drive Through:  3,000 square feet of gross floor area
2. Shopping Center/Strip Center:  6,000 square feet of gross leasable area
3. Gas Station with a Convenience Store:  7 Vehicle Pumps
4. General Office Building:  67,000 square feet of gross floor area
5. Single Family Home Subdivision:  90 Units
6. Apartment Building:  150 Units
7. Owned Condominium/Townhouse Development:  190 Units
8. Drive through Bank:  2,000 square feet of gross floor area
9. Manufacturing Plant:  144,000 square feet of gross floor area
10. Light Industrial/Warehousing:  185,000 square feet of gross floor area

 

 

Why a traffic engineering blog?

I didn't know this until I was an undergraduate in the civil engineering department at the University of Minnesota, but there are actually engineers who try to improve the safety and efficiency of traffic.  This is news to most of the traveling public. 

After a few traffic engineering courses, I decided this was for me.  Improving people's daily commute is a pretty noble cause.  Plus many polls around the country are showing traffic has surpassed crime as the number one community issue.  Talk about job security!

So why a blog?  There are a lot of traffic questions out there and I haven't been able to find a central resource.  So, as a working traffic engineer (Spack Consulting and Traffic Data Inc.) with a background as both a government employed engineer (City of Maple Grove) and a consultant, I decided to pick up the torch.  My goal for the blog is to become an interesting and informative resource for developers, engineers, and anyone who has a question about traffic.