One of my first articles for streets.mn was on Bloomington’s Four Lane Death Roads, (four lane undivided roads) written in response to Bill Lindeke’s introductory article on Four-Lane Death Roads. Four years later it’s time to revisit the subject with updates and additional background material.
The Problem With Death Roads: Conflict Points
Imagine a typical trip down a Death Road. You’re driving down the right lane. Pretty soon there’s a bus stopped or a brave, fearless bicyclist in the lane, so you move into the left lane. Then a car is at a dead stop waiting to make a turn, so have to move back into the right lane. But stopping in a traffic lane to turn is a good way to get rear ended, as well as causing friction and other motorists to make abrupt lane changes, another way of inviting crashes. Plus the motorist waiting to turn is going to get anxious, fearing being rear-ended if he stays their to long, so at the slightest break in traffic s/he guns it, hopefully not hitting any cars or pedestrians in the process.
Engineers like to talk about “conflict points”, where two motorist might try to occupy the same place at the same time. A Death Road doubles the conflict points for through movements at an intersection.
Death Roads also double the conflict points for turning movements. Red is through traffic and blue is turning traffic. You can see at the bottom left the motorist in the red car moves out of the left lane to avoid the blue car that is stopped in the through lane to make a turn, potentially hitting a car in the right lane Father up the diagram you see a motorist going s could rear-end a motorist stopped to turn in either direction on the through lane. At higher volume intersections a right turn lane is appropriate to remove a further conflict point.
The Problem with Death Roads: Sight Distance
Another problem is with turning traffic: a car in the left lane can block the view of a car in the right lane from a motorist waiting to make a left turn.
After writing the original article, the inevitable happened: a pedestrian fatality on 86th Street and Nicollet Avenue. The driver of a southbound Xcel Energy truck going straight tried to make an evasive maneuver to avoid a northbound left turning car that failed to yield, but instead wound up losing control and plowing into a signal pole on the southwest corner, knocking it over. A man that was just standing there on the corner pork chop island waiting for a bus was buried under the whole mess. As typical once the scene was cleaned up and the next dramatic story came about the news media stopped reporting on the investigation, so we don’t really know what happened, but I strongly suspect it was the sight distance issue (there was another car waiting to make a southbound left turn)
Obviously the best solution is to get rid of Death Roads entirely. Convert the road to three-lanes, or even two in a “road diet”, or if that is not possible due to high traffic volumes, add a center turn lane to make a five lane road. This doesn’t mitigate the sight distance issue, but does eliminate some of the conflict points between vehicles. The threshold between roads that need lanes removed vs a lane added is variable and disputed. Numbers given without unduly delaying people in cars range from 10,000 to 20,000+ vehicles per day in various studies. The FHWA (Federal HighWay Administration) suggests the following volumes:
Under 10,000: Great Candidate in Most Instances.
10,000-15,000: Good Candidate in Many Instances
15,000-20,000: Good Candidate in Some Instances
20,000+: Feasibility Study Required, Some Successes By Some Agencies
Factors such as heavy volumes of turning traffic increase that number. Eventually you wind up with so many motorists stopped to make a turn that you only have one usable lane each direction anyway. Numerous traffic signals and stoplights decrease that number, because you’ve substantially increased the queue length for through traffic. Unusually heavy peak use also decreases that number. In Minnesota, 15,000 vehicles per day has been the de facto upper limit, due to a state funding rule that requires two through lanes be provided at that level unless a traffic study proves that it will operate with acceptable level of service with fewer lanes. Generally, a full traffic study is outside the scope of routine mill and overlay projects.
Some Successes and Failures in Bloomington
At the time of my first article, the road diet policy (also known as “traffic calming”) was strictly limited to collector streets. But there were plenty of arterial streets under the magic 15,000 number where a road diet is generally considered workable in Minnesota. The only Death Roads above 15,000 vehicles per day were Old Shakopee Road between Normandale Avenue and France Avenue, and Normandale Avenue near I-494. That part of Normandale Avenue has since added a median and left turn lanes (as well as off-road trails for bicyclists), and the city has in some cases road-dieted arterials.
The Portland Avenue project, led by Hennepin County, was a significant development. There’s still some old, grumpy Bloomington residents who feel it’s their constitutional right to be able to drive down Portland Avenue at 50 mph 24 hours a day, even if more pedestrians are killed and bicyclists are limited to the sidewalk. They made their presence known in the public meetings, so I made sure to show up to show my support for the project. Ultimately the road diet happened. Here are some before and after photos across from Valley View Park, home of a large number of ballfields and the municipal swimming pool.
As a potential encore, we have Nicollet Avenue, which even has some existing 5-lane sections. A mill and overlay is required this fall due to to Centerpoint gas main work, and the idea for doing a road diet didn’t occur to them in time to do the study, so it will remain a death road for now. But if the results of a traffic study are favorable, they might actually grind off the new markings and restripe it as soon as next summer.
At the same time there’s been some failures. Lyndale Avenue south of 102nd was redone with three lanes, but north of 102nd was redone as a Death Road. Responses I got from the engineer were “there’s more traffic near 99th” and “the bicycle lanes wouldn’t connect with anywhere”. This despite already having been identified for an on-street bicycle facility in Bloomington’s alternative transportation plan. And I guess connecting the east-west bicycle shoulder system to a major business district isn’t “anywhere”. Portions of 90th and 94th streets have been also mill and overlaid and stayed Death Roads.
As for 106th Street, this is a special case. A traffic study concluded that due to peak volumes, two eastbound through lanes are required despite overall volumes being below 15,000. Meanwhile the upcoming I-35W project should have provided an opportunity to reconfigure the road. The FHWA is also requiring two westbound lanes at the interchange so that a double left off northbound I-35W ramps can be added in the future if needed. The attitude of the city seems to be “if we need four through lanes, and a traffic study shows that we don’t need additional turn lanes, why build them?”. So we’re stuck with a 1960s Death Road design here.
Beyond Road Diets: Building a Better Bloomington for Bicycles
As good as road diets are, the limitation is there are quite a few bicyclists who still not use the new shoulders, either sticking to the sidewalks, or just not riding at all. I don’t blame them for wanting more than a thin layer of paint separating themselves from motor vehicles. To the extent I bicycle around Bloomington at all, I won’t ride the shoulders, sticking to the sidewalks myself. In Bloomington, it seems the vast majority of bicyclists of all ages still ride on the sidewalks on both Death Roads and dieted roads. We need to do better by building more off-road paths in future projects. We also need to start fixing problems with our sidewalks, but that’s a topic for a future article.
Thanks for this Monte. The safety case for 3-lane cross-sections is pretty convincing to me. I hope there are folks in Bloomington that see the benefits here.
As a Bloomington resident I fully support road dieting. I bike often, and choose whether to be on the road or on the sidewalk on a case by case basis. If there’s a wide shoulder lane I’m likely to use it unless there is heavy traffic going above 35 miles per hour. If its a thin shoulder lane I’ll use it if traffic is light and lower than 35 miles per hour.
Its disappointing that 102nd Street between Normandale and France wasn’t road dieted. Yes there’s a lot of school traffic, but there’s also a lot of kids and teenagers walking or biking to/from school. Combine that with high schoolers going to/from Jefferson who think they’re above the law and you have a recipe for disaster.
While I do support bike lanes and wider sidewalks, its also important that we do better to educate drivers on why they need to be respectful to pedestrians and bikers, and to emphasize stopping before the stop sign instead of in the middle of the crosswalk because you never know when a walker or biker is approaching. Numerous times people stop in the crosswalk and are oblivious to me approaching. Sometimes they see me and back up, and sometimes I have to slow down and wait and the driver never notices me or they do and they’re shocked to see someone using the sidewalk.
Nice article, Monte. I am struck by how many black lines are still left on that map. On the one hand, Bloomington has converted a lot of streets — on the other, they just had some absolutely crazy 4LDRs to begin with. Around the Auto Club Rd / Overlook Dr area, they had some roadways with less than a thousand cars a day on four-lane roads.
One slight correction: a number of those roads in the SW part of the city were actually converted to 2-lane with wide shoulders.
I’ll argue that the 4-lane to 3-lane restriping is not optimal geometry for anyone. I believe (someone please fact-check this!) that the standard Bloomington 4-lane road is 44′ wide, with 4x 11′ lanes. Restriping it to a 3-lane configuration is done with 2x 5′ shoulders, 2x 11′ traffic lanes, and 1x 12′ turn lane (5+11+12+11+5 = 44). A 5′ shoulder – considering all the roadside debris – is hard to bike on. The outer 3-4 feet are generally not safe for biking. A better geometry would be taking a couple of feet from the center turn lane and giving it to the shoulders (6+11+10+11+6), or taking a foot off each travel lane (6+10+12+10+6). The incremental foot on the shoulders would be extremely beneficial to bikers, without significantly impacting the road use.
I like your 11/10/11 plan. I’ll take it!
Portland Ave the layout I saw was 5.5-11-11-11-5.5, not sure about 86th or the other three lane roads that the city has done themselves, but most of the minor city roads have actually gone down to two lanes in a 8-14-14-8. These shoulders aren’t signed or promoted as bicycle lanes for political reasons and because they don’t all meet the standard for bicycle lanes since in some cases off-peak on-street parking is allowed as it was before.
I agree 6+11+10+11+6 is preferable. In my opinion, Portland should have been two lanes with buffered bike lanes — simply because volume is so low, there is really not a need for a dedicated turn lanes into residential driveways.
Note that Nicollet is a bit wider, so there you can do 3x 11′ lanes and still have two 7.5′ shoulders.
86th is noticeably tight with 5′ shoulders — especially when one of those bulky round catch basins eats up half of it.
A glossary of traffic terminology would be awesome for the greater number of us new to city planning and development. Discussions around the use of Willy Mc Coys parking lot vs city streets to come or go to a new apartment complex approved by city this summer were dubious sounding at best and possibly bogus in worst case. Who. Does. That? ie: turns to meander thru a non road or non thoroughfare which is a shopping/ restaurant/ parking lot en route to work or schools? Who enters a major thoroughfare NOT where everyone else has stop signs and lights? Who follows an arrow leaving their own resident parking lot if it directs them into a commercial parking lot. Traffic folx appeared to be procrastinating the truth. Possibly to appease the noisy Nimby neighbors. Buildings going up anyhow. Will house teachers and firefighters… Mid to lower mid income. Maybe 4 subsidized apartment homes out of the 42. The WorkForce has to reside somewhere reasonably close to work. Traffic monitoring and report seems quite apart from driving realities, rush hours, peoples habits. Concepts and terminology for me hold Lots of new words. Just sayin.