Category Archives: Safety

When drivers pass by, they almost stop completely due to the holes and to avoid car damages.

Speed Control in Israel (updated)

The following appeared across the email transom. The source is unknown. The forwarder stated:

One of my Internet Buddies sent it claiming it to be an Isreali invention. Who knows. Maybe it’s a joke, but none-the-less it appears to be a great idea, unless of course people swerve out of their lane and cause an accident!

When drivers pass by, they almost stop  completely due to the holes and to avoid car damages.
When drivers pass by, they almost stop
completely due to the holes and to avoid car damages.
This is a strategy currently used in Israel as a high-speed control. It is more economical than using cameras, radar, police officers, etc.
This is a strategy currently used in Israel as a high-speed control.
It is more economical than using cameras, radar, police officers, etc.
They move them around every day!
They move them around every day!

Update: part of an ad campaign by Pioneer Suspension.

Hi Dr. Levinson, I searched for the message that was written on the road in the pictures and came up with this:

http://www.hoax-slayer.com/fake-potholes.shtml

Keeping the Green Line safe – The Minnesota Daily

Things I would not be allowed to say were I a public official … in The Minnesota Daily Keeping the Green Line safe :

“…

“Light rail trains empirically kill more people than buses,” said David Levinson, a civil engineering professor and transportation studies expert.

Metro Transit spokesman John Siqveland said the Green and Blue Lines were built with safety in mind and that the Green Line will generally run slower since it will travel through more densely populated areas.

The vast majority of light-rail and streetcar systems around the country run on street level, Siqveland said.

Metro Transit has two train routes and 125 bus routes. Of the 81 million rides Metro Transit gave last year, 86 percent of riders use buses and 14 percent use trains.

Since the Blue Line opened in June 2004, the agency’s buses have had 6,979 incidents, which resulted in five deaths. Like the light rail, the majority of collisions involved motor vehicles. Of the 145 bus incidents involving pedestrians, four were fatal.

“Buses serve a lot more people and run a lot more miles … but have fewer fatalities,” Levinson said. “The [fatality] rates are obviously much higher for light-rail trains. Still, it’s a lot safer than driving a car.”

The 11-mile light-rail route connecting downtown Minneapolis to downtown St. Paul is decades in the making and cost $957 million.

“It’s been built, so it’s too late. It’s an at-grade light-rail facility — there’s nothing we can do about it without spending another billion dollars,” Levinson said. “We don’t operate in this world to maximize safety and only safety; we have trade-offs.””

The low-friction nature of train travel makes it efficient, but it also makes stopping a problem, said Stephen Zitzow, Minnesota Traffic Observatory laboratory manager.

Each train weighs about 300,000 pounds, and bringing one to a complete stop from 55 mph takes the length of two football fields. At 20 mph, it takes 81 feet, Siqveland said.

“It doesn’t have the option to swerve out of the way of someone in the way,” Zitzow said. “The difference here is that most vehicles can maneuver much more than a light rail, which is stuck.”

Central Corridor project spokeswoman Laura Baenen said the Green Line will begin running before the Major League Baseball All-Star game at Target Field in July.

Baenen said the Metropolitan Council has taken many safety considerations, including creating a pedestrian mall and using posters and community educators.

Baenen said a street-level light-rail track is less costly than an underground or elevated one, which was “prohibitively expensive.”

Siqveland said part of the Metro Transit safety campaign will have links to its website posted at every train stop.

When asked if he’d visit the website, graduate student Hill said he most likely wouldn’t.

“If I am an example,” he said, “[other students] probably will not.”

See also this (presented at TRB) (which is a bit dated), still I think it is largely accurate. Another interesting tidbit is that urban autos kill relatively few people (on a per mile basis). More auto deaths (on a per capital, per mile, etc. basis) are rural.

Also note that the APTA Public Transportation Fact Book (p.26) does not break out LRT deaths, lumping that with rail transit. I wonder why.

Inform pedestrians, not drivers

Inform pedestrians, not drivers:

From Sacha Kapoor and Arvind Magesan (pdf):

Most empirical studies on the role of information in markets analyze policies that reduce asymmetries in the information that market participants possess, often suggesting that the policies improve welfare. We exploit the introduction of pedestrian countdown signals – timers that indicate when traffic lights will change – to evaluate a policy that increases the information that all market participants possess. We find that although countdown signals reduce the number of pedestrians struck by automobiles, they increase the number of collisions between automobiles. We also find that countdown signals caused more collisions overall. The findings imply welfare gains can be attained by revealing the information to pedestrians and hiding it from drivers. We conclude that policies which increase asymmetries in information can improve welfare.

Hat tip goes to @m_sendhil.

(Via Marginal Revolution)

Eliminate the bi-annual time change caused by Daylight Savings Time

A new petition at WhiteHouse.gov asks to Eliminate the bi-annual time change caused by Daylight Savings Time :

“Daylight Savings Time is an archaic practice in our modern society.
The original reasons for the policies are no longer applicable, and the most cited reason for keeping DST (energy savings) has never been shown to be true.
Some industries still like DST (like sporting equipment retailers), but there are many more who dislike the changed hours (like television).
The real issue, however is not the later hours or extra sunlight. Studies have shown that changing the clocks is responsible for health problems (including increased heart attack and vehicular accident risks) and leads to hundreds of thousands of hours of lost productivity in workplaces across the country. Also: It’s really annoying.
We should either eliminate DST or make it the year-round standard time for the whole country.”

While our results on the traffic safety consequences are mixed (DST reduces crash rates but increases traffic) it nets that DST enhances safety. Still, I tend to agree with the petition, we could achieve the benefits by having a fixed adjustment year round. And if people want to switch behaviors relative to the clock, good for them. Me, I would eliminate timezones too, and have one global time, so I wouldn’t have to go to work until 14:00 GMT and could sleep in every day.
Reference:
Huang, Arthur and David Levinson (2010) The Effects of Daylight Saving Time on Vehicle Crashes in Minnesota Journal of Safety Research 41 513-520.

With more total driver’s licenses, women passing men on the roads

Aimee Blanchette @ Strib: With more total driver’s licenses, women passing men on the roads :

The jokes about dreadful female drivers can officially take a back seat.
For the first time ever, more women than men have driver’s licenses nationwide. This gender gap reversal means safer roads and less pollution.
That’s according to the University of Michigan’s Transportation Research Institute, which says that in 2010, 105 million women held licenses, compared with 104 million men. Women are more likely to purchase “smaller, safer and more fuel-efficient vehicles” and “drive less and tend to have a lower fatality rate per distance driven,” said Michael Sivak, the study’s co-author.
The stereotype, however, has been a joke as long as women have been driving.
“It wasn’t true and I don’t think people find it funny anymore,” said David Levinson, a professor in the Department of Civil Engineering at the University of Minnesota.“Statistics have long shown that the average woman is a slightly safer driver than the average man.”

Gas Prices and Traffic Safety

My colleague and co-author Guangqing Chi on Gas Prices and Traffic Safety on video:

Some of the work he is describing is published in these papers:

One interesting policy implication is that as gas prices go up, average insurance rates should go down, since risk is dropping. Whether it goes down by cohort, or just overall as the shares of various cohorts traveling changes, is unclear.

There’s no business like snow business | streets.mn

Cross-posted at streets.mn: There’s no business like snow business :

There’s no business like snow business

 

Snow is a popular topic in the Great White North. Julie wrote A Salute To Snowy Streets, while Reuben discovers What snow teaches us about roads .

I had a media inquiry a year ago on “Why we become such bad drivers when it snows”, I didn’t take it, but the question is interesting in a sense. Unlike the rain in southern California, it always snows in Central Minnesota, so this is a recurring question.

Several things happen when it snows:

Capacity

1. Roads are slipperier and require longer braking distances. People recognize that roads are slipperier and give increased spacing (following headway in the jargon) to the car in front. Instead of following at a 2 second headway (remember the 2 second rule from Driver’s Ed), they may follow at a 3 second headway. Since there are 3600 seconds in an hour, a 2 second headway implies 1800 vehicles per hour (traffic engineers will note of course that capacities per lane on freeways are often greater than this in good conditions, implying a shorter than 2 second headway). A three second headway implies a service flow or capacity (Qmax) of 1200 vehicles per hour. If the underlying demand (those who want to use the bottleneck at that time) remains unchanged at 1800 vph (say it snowed surprisingly in the middle of the day), then instead of serving 1800 cars, a bottleneck would serve only 1200 in an hour. This implies a queue 600 cars long. That is non-trivial.

2. Roads are slipperier. People recognize that roads are slipperier and drive slower to reduce braking distances, especially on roads which curve.

SpeedReduction

Kyte et al. “The effects of poor weather conditions on free-flow speed on a rural Interstate freeway are considered. It was found that free-flow speed is affected by pavement conditions, visibility, and wind speeds. It is also suggested that poor weather conditions occur with some degree of frequency in a number of U.S. cities and that the effects of poor weather should be considered in such cases as part of capacity and level-of-service analyses.”

3. Roads are slipperier. People insufficiently recognize that roads are slipperier and instead of giving increased spacing choose to crash into the vehicle in front of them. This temporarily reduces capacity to zero as the drivers sort out the situation.

Crash

Khattak and Knaap “significant increase was observed when winter snow event injury and noninjury crash rates (crashes per million vehicle kilometers) were compared with equivalent winter nonsnow event injury and noninjury crash rates. The data were then analyzed for injury occurrence. Results of a logit model indicated that crash injury occurrence on Interstate highways in Iowa depended on traffic, road geometry, and number of vehicles involved in a crash. Another finding from the logit model was that crashes during snow events were less injurious compared with equivalent nonsnow event crashes. Snow event–specific crash data were then analyzed to study the effects of snow event elements (e.g., snowfall intensity) on injury occurrence in vehicular crashes.”

4. Snow does in fact reduce demand. People choose not to go out when it snows. Arthur Huang and I conducted some research on Minnesota travel patterns statewide and found these elasticities (so if it snows, there is a 5.9% reduction in demand and 63.9% increase in crashes in the 3am to 9am time period). The reduction in demand seems to be less than the reduction in capacity, so queueing increases on roads at or near capacity in the absence of snow.

DemandReduction

Demand Crashes
3am-9am -0.059 0.639
9am-3pm -0.092 0.926
3pm-9pm -0.115 0.752
9pm – 12am -0.091 0.814
all day -0.079

A. Huang, D. Levinson / Journal of Safety Research 41 (2010) 513–520

Others have found significant results as well:

Datla and Sharma “The commuter roads experience lowest reductions in traffic volume due to cold (up to 14%) while the recreational roads experience highest reduction (up to 31%). Impact of cold on off-peak hours (-10% to -15%) is generally higher than peak hours (-6% to -10%) for commuter roads and an opposite pattern is observed for recreational roads (peak hour reductions of 30–58% and off-peak hour reductions of 18–30%). A clear indication of reduction in traffic volume due to snow is also observed for all types of highways.”

So I wouldn’t say we become bad drivers. We are bad drivers, we just reveal it when the environment changes to the unexpected.

(This presents one more argument for robot cars. They can’t overcome the physics of braking distance or eliminate congestion, but they can in principle better assess road conditions and be less likely to crash.)

References:

Al Hassan, Y., and Derek J. Barker. “The impact of unseasonable or extreme weather on traffic activity within Lothian region, Scotland.” Journal of Transport Geography 7.3 (1999): 209-213.

Huang, Arthur, and David Levinson. “The effects of daylight saving time on vehicle crashes in Minnesota.” Journal of Safety Research 41.6 (2010): 513-520.

Khattak, Aemal J., and Keith K. Knapp. “Interstate highway crash injuries during winter snow and nonsnow events.” Transportation Research Record: Journal of the Transportation Research Board 1746.-1 (2001): 30-36.

Datla, Sandeep, and Satish Sharma. “Impact of cold and snow on temporal and spatial variations of highway traffic volumes.” Journal of Transport Geography 16.5 (2008): 358-372.

Kyte, Michael, et al. “Effect of weather on free-flow speed.” Transportation Research Record: Journal of the Transportation Research Board 1776.-1 (2001): 60-68.

Rooney Jr, John F. “The urban snow hazard in the United States: An appraisal of disruption.” Geographical Review (1967): 538-559.

Smith, Brian L., et al. “An investigation into the impact of rainfall on freeway traffic flow.” 83rd annual meeting of the Transportation Research Board, Washington DC. 2004.
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The impact of gasoline price changes on traffic safety: a time geography explanation

TimeGeographyFigure
Recently Published:

  • Chi, Guangchi, Jeremy Porter, Arthur Cosby and David Levinson (2013) The impact of gasoline price changes on traffic safety: a time geography explanation. Journal of Transport Geography Volume 28, April 2013, pp. 1-11 [doi]

    The impact of gasoline price changes on traffic safety has received increasing attention in empirical studies. In this study, we use time geography to provide a theoretical framework for examining the effects of time-varying fluctuations in gasoline prices and their relationship to traffic safety in a case study of Mississippi from April 2004 to December 2010. Application of time geography theory suggests that gasoline prices act as one type of capability constraint of the space–time path. As gasoline prices increase (that is, as the capability constraint becomes stronger), we hypothesize traffic crash rates decrease, and they decrease more for groups for whom the constraint is stronger. The results corroborate the hypotheses and suggest that gasoline prices have stronger effects on reducing less severe crashes and negligible effects on reducing fatal crashes. Gasoline price effects on reducing crashes start at a 9-month lag, peak at a 12-month lag, and diminish after an 18-month lag.

As commentary, the recent increase in crashes this last year (2012 vs. 2011) as the effects of the recession wane (and the budgetary constraints on travel relax) provides corroborative evidence.

Positions: Ning Li, Virginia DOT

NingLiRisingStar

Continuing on where are they now:
Nexus group alumnus Ning Li and Nexus group alumna, Wenling Chen, his wife, both work for Virginia DOT and are proud parents of 7 month old Jay. Ning was just selected by the National Safety Council as a Rising Star of Safety, one of the few in transportation. This is the second major safety award Ning has won.
The reason given was:

“In an effort to develop strategies for reducing Virginia’s roadway departure crashes, Ning identified and addressed a major defect in Virginia’s RD [Roadway Departure] crash data. Through collaboration with national peers, Ning verified the national scope of the defect and brought the issue to the attention of the Federal Highway Administration. As a result, FHWA released an official memorandum in 2009 on a new RD crash definition and criteria. Not only were Ning’s suggestions adopted in the memo, FHWA staff also acknowledged his ‘significant contributions to the important highway safety effort.’”