101 Worst Traffic Engineering Misteaks

Over the years, traffic engineering, the science of moving automobile traffic safely, has improved. But quite a few mistakes (or is it "misteaks" instead?) have been made. These are usually made by people without enough training. This includes politicians, who have no training at all in the subject, yet consider themselves experts solely because they were elected to office.

Note: MUTCD = US Department of Transportation Manual of Uniform Traffic Control Devices.

Here are the worst of these dillies, with the worst of the worst first:

1. Yellow trap at traffic signals (click for more)
   • This has probably caused more auto accidents since 1955 than any other engineering mistake. Thank the US Department of Transportation for prohibiting this hazard in 2003. Too bad it still exists.
2. The three-lane two-way highway with the shared center lane
   • This probably caused more auto accidents before 1955 than any other engineering mistake.
3. Using the vehicle extension interval to substitute for properly placing the detector farther from the stop line
   • This can trap a vehicle with a longer following distance in its dilemma zone (can't stop in time, can't clear the intersection).
4. Weaving major movements across each other (Weaving is streams of traffic changing lanes across each other)
   • This causes many wrong turns and dangerous maneuvers on an interchange. Each driver is unable to change into the correct lane, because other traffic is in the way.
5. Freeway entrances without acceleration lanes
   • This causes many drivers to either get into an accident or become trapped on the entrance ramp.
6. Bike boxes politically please cyclists, but cause hazards when large vehicles are present (see image)
   • The truck waiting for the green light keeps the driver of the purple car and the cyclist intending to turn left from seeing each other.
7. Leaving a gap in a needed freeway, to please politicians or pressure groups (e.g. Breezewood PA, Trenton NJ)
   • This causes drivers many headaches to please greedy politicians and individuals. It should be illegal.
8. Multiple uses of the same lane (e.g. left turn, passing, and weaving)
   • This is dangerous, because a driver in the middle of a pass suddenly finds a car waiting to turn left in the same lane.
9. Traffic signal left turn arrows without any clearance periods or with hidden (invisible) clearance periods
   • Thank the US Department of Transportation for requiring clearance periods in 1961 and visible clearance in 1978.
10. Violating the dilemma zone by allowing phases to stop timing at the first gap or to reach a short phase maximum
    • This causes accidents when vehicles on high speed roads are trapped in their dilemma zones.
11. Designing intersections that don't move traffic well (see image)
    • This happens two ways.
      1. Money is saved on acquiring the land.
      2. New features were patched into an existing design.
12. Using green arrows for permissive turns
    • This happened before there were standards, but many nonstandard installations survived into the time when standards existed.
13. Not checking approaches without left turn signals for yellow trap
    • Most cases of yellow trap are caused by this, because the approach is ignored in the analysis.
14. Green arrows turning across pedestrian crossings with walk or flashing don't walk signals
    • This is usually the result of misreading an ambiguously worded requirement in the MUTCD.
15. Green arrows faces used for lane use control, instead of lane use signs and circular greens
    • This is usually a misuse of a traffic control device to save money.
16. Carpool lanes (reduce overall capacity)
    • This is a way for greedy government to push its religious beliefs on others.
17. Toll lanes to bypass traffic (reduce overall capacity, abet government greed)
    • This is a way for greedy government to push its religious beliefs on others.
18. Railroad, drawbridge, or emergency vehicle preemptions that cause yellow trap
    • This is caused by an inability to provide safe indications, because until recently they were not available.
19. Red light cameras (cause more accidents, wrongly intended to raise revenue, and remove the right to cross-examine)
    • This is a way for greedy government to push its greed on others.
20. Movements not provided at traffic interchanges
    • These attempts to save money cause anxiety, wasted mileage, and traffic accidents, as drivers end up going in directions they did not want to go. Often ramps are omitted to preserve some useless landmark.
21. Interchange ramps too close together
    • This is a chief cause of bottlenecks on badly designed freeways.
22. Traffic signal clearance interval too short
    • This is usually government incompetence, but often government greed endangers drivers with it for more ticket revenue.
23. Violating the dilemma zone with detectors placed too close to the stop line for the speed limit used
    • This is usually done to save money. Sometimes it is done because the cable can't carry the detector signal far enough. But it is better to move the detector amplifier, rather than have traffic accidents.
24. Signs installed in the wrong place (e.g. post mounted signs intended for overhead use)
    • Too many laymen design traffic control installations. But some politicians force the issue by prohibiting overhead signs for aesthetic reasons.
25. Setting signal progression to favor drivers using government offices, rather than the major movements
    • This is the worst in government greed. It favors the few over the many. When can we finally rid ourselves of selfish government employees?
26. Lane drops in between other lanes going the same way
    • This is bad design. It confuses drivers. If lanes must be dropped in the middle, it would be better to use frontage roads or scissors ramps than dropping lanes in the middle of the road.
27. Inadequate signing for which lane to use for which destination
    • This causes a lot of last-minute lane changes, endangering other drivers.
28. Intersections spaced too close
    • This causes many kinds of extra conflicts, signal phases, and hazards.
29. Setting speed limits by legislation, rather than by solid engineering
    • This causes unnecessary lawbreaking by competent drivers, and causes too many passing conflicts.
30. Setting a speed limit lower than the design speed of the road
    • This causes unnecessary lawbreaking by competent drivers, and causes too many passing conflicts.
31. Driveways too close to intersections
    • Vehicles entering and exiting driveways near intersections cause unexpected conflicts, block lanes while drivers wait to turn, and activate the wrong detectors at traffic signals.
32. Bad geometry
    • This creates hard-to-negotiate poor vehicle paths. This is often due to a reluctance to take property.
33. Inadequate sight distance
    • This is often due to a building or trees placed too close to the road
34. Signs hidden behind trees, telephone poles, or other signs
    • This is usually caused by sticking too well to the guidelines for sign placement, instead of adjusting the placement to fit actual conditions.
35. Insufficiently posted speed limits
    • This causes drivers who turn from side roads to not know the speed limit for miles. The entire traffic system must be made such that a stranger to the area can drive it correctly.
36. Substandard sign sizes
    • They cause drivers to miss needed information, because they can't be read at speed.
37. Traffic control devices used wrong
    • This endangers drivers who expect the standard meanings, and violates the MUTCD.
38. Restricting trucks to the same lanes that traffic must use to exit and enter the freeway
    • This is a good way to cause more accidents, just to favor the speed demons.
39. Different speed limits for different kinds of vehicles on the same road
    • This is guaranteed to cause more accidents due to increased passing conflicts.
40. Reserving a lane for passing
    • This reduces the capacity of the road, just to favor the speed demons.
41. Curves too close to intersections
    • This causes insufficient sight distance, and causes drivers to turn into the wrong lanes.
42. Using "3-WAY" supplemental plates on stop signs with one approach that does not stop
    • Causes driver confusion and accidents, and violates the MUTCD.
43. Placing traffic signs to close to intersections
    • Turning drivers need to see the road there, and miss the signs.
44. Locating traffic signs where it is ambiguous which drivers they are meant for
    • This is again usually a case of not adapting sign placement standards to meet conditions.
45. Using span wires to hold up limited visibility signals
    • This causes driver confusion, when drivers see the wrong signal faces and act on them when a high wind blows.
46. Allowing turns on red where left turn signals send traffic into all lanes
    • This causes unexpected conflicts. The turn on red should be prohibited.
47. Causing "second yellow trap" by ending a permissive turn while an opposing right turn has a green arrow or flashing yellow arrow
    • The right turn should be stopped, and then restarted, or it should have its own merge lane.
48. Making intersections too small for trucks to be able to turn
    • This is a stupid design intended to favor pedestrians, at the expense of the trucks bringing the products to them.
49. Refusal to use one-way streets to improve traffic flow and facilitate signal progression
    • Wastes traffic capacity, and wastes energy with unnecessary stops.
50. Using simultaneous signal synchronization with short block lengths
    • Wastes energy in unnecessary stops.
51. Using yellow paint to designate a prohibition
    • Yellow paint no longer means a prohibition. Red paint has that meaning. Yellow paint separates traffic moving in opposite directions.
52. Sending unsuspecting motorists from highways onto side streets, to handle traffic leaving a concert or a sporting event
    • This is an unfair treatment of strangers to the area in an attempt to favor the people attending useless events that aid government coffers while shrinking the economy.
53. Not clearly posting a detour
    • This saves the contractor a few dollars, but sends motorists wandering and wasting fuel.
54. Not posting what street a detour is for on the signs
    • This also saves the contractor a few dollars, but also sends motorists wandering and wasting fuel, especially if two closures use the same detour route.
55. Wrongly choosing a detour route that trucks can not maneuver through
    • This causes traffic jams, and also causes truck drivers to leave the marked truck routes to avoid the place they can't maneuver.
56. No provision for directions back to a freeway for traffic sent off a freeway closed by an accident
    • This sends drivers into unmarked territory. Often they have secondary accidents while trying to find their way back to the freeway.
57. Unnecessary slowing high speed traffic by allowing schools to be built on major highways
    • This is stupidly putting government first, at the expense of everyone else. It also wastes energy.
58. Insufficient school zone signs that do not notify drivers turning from side streets about the school zone
    • This is pure government greed on both ends:
      1. Spending less money on traffic signs.
      2. More ill-gotten revenue from traffic tickets paid by tricked drivers.
59. Flashing lights on school zone signs placed where traffic on the main road can see them, but not side-road drivers
    • This is also pure government greed on both ends:
      1. Spending less money on the flashing lights.
      2. More ill-gotten revenue from traffic tickets paid by tricked drivers.
60. Putting on-street parking on major thorofares
    • This blocks traffic every time a car enters or leaves a parking space.
61. Not providing enough shoulder to keep a disabled vehicle away from traffic lanes
    • This is a foolish economy, trading money saved on leaving out the shoulder for increased accidents.
62. Making curbs too high, damaging vehicles that would otherwise be stopped without damage
    • Is this a misguided attempt to save money by allowing more layers of pavement before rebuilding curbs, or a misguided attempt to protect pedestrians from wayward vehicles?
63. Requiring through traffic to change lanes to stay on the through route
    • This causes drivers who don't notice or can't make the change to waste fuel by driving out of their way.
64. Making traffic lanes too narrow
    • This causes marginal friction conflicts that are not necessary, and often causes accidents.
65. Not providing left turn lanes where they are needed
    • This causes unnecessary traffic backups, and precludes the use of some more efficient traffic signal phasings.
66. Placing aesthetics above safety and function
    • This is one of the worst demands politicians can impose on engineers. Aesthetics are totally worthless, and often cause traffic accidents.
67. Not installing needed overhead signs, because government officials want to preserve a view
    • This is government vanity at its worst. Aesthetics belong in the garbage can if they cause even one traffic accident.
68. Letting the capabilities of the detector signal cable limit the distance the detector is placed from the stop line
    • This is saving money on the budget, while causing more traffic accidents with drivers are caught in dilemma zones.
69. Setting traffic controls at the request of government or nonprofit road users
    • This is government rearing its greedy head again, at the expense of drivers and energy savings.
70. Protecting emergency vehicle drivers with designs that create hazards for other drivers (e.g. yellow trap)
    • This misguided desire to protect public servants endangers others. Design the yellow trap out of the signal.
71. Making the traffic circulating on a traffic circle yield to entering traffic
    • This is a plan guaranteed to fail. Traffic will lock up in it. Entering traffic should yield.
72. Unsafe installation of bicycle lanes and paths
    • Bike lanes that are wrongly installed are more dangerous than the absence of bike lanes.
73. Mass transit systems that block other vehicles, wasting fuel
    • What good is the saving of fuel from the use of mass transit, when the overall effect is that more fuel is wasted?
74. Allowing mass transit vehicles to destroy signal progression by blocking vehicles or preempting signals
    • This is more of the same. Favoring the mass transit vehicles wastes more fuel overall.
75. Adjusting signal progression for mass transit, rather than for most vehicles
    • This is even more of the same. Favoring the transit vehicles wastes more fuel than not having a transit system would.
76. Improper or absent preemption for railroad crossings and drawbridges near signalized intersections
    • This is the way to get a lot of people killed, as cars forced to stop on the tracks or the bridge are destroyed.
77. Failure to design to accommodate long vehicles, including double trailers
    • This is false economy, because more fuel and labor must be consumed moving goods to smaller vehicles to make the deliveries.
78. Requiring highway traffic to stop for recreational trail users
    • This is the biggest waste of resources for the most trivial reason I can think of.
79. Requiring or allowing trees to be planted too close to the road
    • Trees should be placed at least 20 feet away from the road, to improve sight distance and prevent pavement damage from roots.
80. Any ambiguous traffic sign, signal, marking, or other traffic control device
    • This will cause drivers to become confused. Confusion leads to wasted fuel and auto accidents.
81. Allowing utility lines to be run lengthwise under major thorofares, rather than alongside them
    • This turns a minor disruption into a major problem when the lines need to be serviced. Place them to one side of the road in the right-of-way.
82. Left turn phases on low volume approaches
    • This is certainly not intended to be efficient. Unless it is there to prevent yellow trap, it is intended to please someone for political reasons. Such uses must be abolished.
83. Giving a low-volume driveway its own exclusive signal phase
    • This is often done when a driveway forms the fourth leg of an intersection. But a better plan is to give a leading left turn phase in the opposite direction, then give both directions circular greens. This reduces delay and saves fuel.
84. Insufficient vertical and/or horizontal clearances for large vehicles
    • This causes large vehicles to choose alternate routes to avoid places where they don't fit. Such actions waste fuel. And some drivers miss the signs and hit the obstruction.
85. Misplacing the word "only" (an adjective, not an adverb) in signs
    • This confuses people who know the rules of English. "Only" is not an adverb. It modifies the word following it, not the verb.
86. Allowing environmentalists to inject their religious beliefs (rather than facts) into traffic control
    • Their beliefs, if implemented, usually cause others to waste fuel.
87. Allowing citizen pressure groups or layman politicians to override MUTCD specifications or the decisions of trained engineers
    • Such misguided practices usually end up costing people more in fuel bills, as the most efficient solutions are usually discarded in the process.
88. Concentrating on stopping traffic, rather than moving it
    • This is guaranteed to waste more fuels. But it is the typical wrong response of a layman given the job of controlling traffic.
89. Designing cities with additional diagonal streets
    • This often looks good on paper, but it is a nightmare to implement. The bottlenecks are usually multiphase signals with six legs.
90. Ignoring the use of evergreen trees as a sound blocking medium
    • This is a cheap, easy to maintain solution. But the officials must wait several years for results.
91. Expecting mass transit to handle more than 10 percent of the trips
    • It would help if the transit system actually went to the places the other 90 percent of the trips go to. Except in the 15 largest cities in the US, mass transit can't afford to cover even 10 percent of the places.
92. Overuse of left-turn phases, instead of considering alternatives (one-way streets or indirect turns)
    • The other alternatives are more expensive, but the fuel savings should pay for the extra paving in a few years.
93. Parking lots marked with the wrong paint colors
    • This results in a savings of less than $100 per parking lot. Parking lots are now required to obey the MUTCD. It should be enforced.
94. Traffic calming devices used to remove traffic from a politician's street
    • This is more political greed. If the politician doesn't like the traffic, he should move.
95. Parking meters and parking time limits
    • These abet government greed, with no real benefit. The shoppers the merchants hope to attract shop elsewhere, where they are not threatened by a time limit or pay parking.
96. Speed bumps
    • Whoever invented this deserves a firing squad. Speed bumps damage vehicles, and they don't slow all traffic, because many drivers find they are less obtrusive at higher speeds. They should be abolished.
97. Misunderstanding the red arrow on a traffic signal, or refusing to allow its use
    • Too many politicians associate an arrow with movement, rather than direction. Fortunately, the drivers do not. If Florida has used red arrows for years without trouble, then maybe some other states can learn from this, and allow red arrows. They are now mandatory for single movement turn signals.
98. Toll roads
    • These reduce overall capacity. The only thing they are good for is fattening greedy government's coffers. They belong to the past.
99. Signs advertising government facilities in areas with billboard bans
    • This is unfair treatment of others wanting to advertise, and shows off the severity of government greed
100. Letting a layman traffic commission make decisions
     • This is like letting an untrained person design a building. It is a disaster waiting to happen.
101. The full cloverleaf interchange, with the weaving of left turn movements
     • It works as long as traffic is relatively low, and left turns are rare. But too often they were installed where the left turns jam up the weaving sections.

Links

• WORST INTERSECTIONS IN BLOOMINGTON INDIANA
• YELLOW-TRAP IN BLOOMINGTON INDIANA
• UNUSUAL TRAFFIC PROBLEMS, HAZARDS, AND SOLUTIONS