The Dangers of Turn Signal Neglect

Whether changing lanes, merging, turning at an intersection, exiting a roundabout, or entering traffic from an acceleration lane, turn signals have a lot of utility for a safety minded, courteous driver.

Unfortunately, it often seems as though many drivers don’t know when to use their signals, or worse, don’t know how to use them.

One of the most common complaints received by SafetyFirst on our Hotline program is “failure to use signals” at roughly 13% of all reported behavior types. 

When you consider that: Improper Lane Change; Failure to Use Signals; Dishonor Right of Way; Weaving in Traffic; Failure to Stay in Lane; and Improper Passing are all somewhat related issues, then the total of these issues jumps to 47.74% of all behaviors reported during 2012.

Commercial drivers seem to have a problem with merging and changing lanes.  I strongly suspect that it’s a combination of issues:

  1. Drivers seemingly get ticketed only very rarely for failing to use their signals; therefore, any given driver’s attitudes about signals are reinforced (if the police don’t care, why should I ?)
  2. Managers rarely, if ever, have a pain threshold over the non-use of signals to warrant training meetings, etc. (see #1, above)
  3. Signal non-use just isn’t seen as a pressing priority by society.  (It fails to get the marketing weight of othermore pressing issues such as drinking and driving or aggressive driving, etc.)
  4. Drivers who are in a hurry may see slower moving vehicles as obstacles in their path.  The need to get there in a hurry can lead to swerving from lane to lane, and despite the obvious risk of failing to signal while driving aggressively operators seem to forget that the signals are there for a reason.
  5. Failure to clear the blind area next to the vehicle (each vehicle’s mirrors can only see select areas based on how they’re positioned – resulting in an area where the driver is effectively “blind” to other vehicles) increases the need to use signals as an additional indicator of an impending lane change, but drivers assume that the other driver will react to their vehicle moving laterally into the lane without the bother of signaling.
  6. Turn signals don’t impart the gravitas of a horn – you can’t release your stress through aggressive signal use the way you can with leaning on your horn (OK, so I’m being sarcastic here, but you’ve got to admit I may be on to something).

Consider the opening sentence of the abstract of a recent (4/16/2012) study (LINK) by the Society of Automotive Engineers (SAE) – “The turn signal is a vital safety feature that is not only required to be built in as standard equipment on all vehicles, but their use by the driver in everyday driving is required by law.”  This makes signals sound pretty important, huh?

Now, take a look at the remainder of the abstract; “Since not all drivers are diligent at properly actuating turn signals in every situation, the use of the turn signal is less than 100%. However, despite the fact that turn signals are a crash prevention feature, no known study relating to turn signal usage rates is available from the National Highway Traffic Safety Administration, nor from the Department of Transportation, nor from any University, nor from other private safety organizations.”  Wow, none of the key data gathering organizations have quantitatively studied the role of turn signals on crashes?  Yikes – that’s like driving blindfolded (well, maybe not, but it’s a significant oversight, isn’t it?)

As a counterpoint, American Transportation Research Institute (ATRI) may have been overlooked by SAE while doing their background research.  You see, in 2005, ATRI published a study (and subsequent update in 2011) titled “Predicting Truck Crash Involvement”.  In this study, they specifically looked at violations received by drivers and projected the increased likelihood of becoming involved in a crash following the ticket.  Their number one issue from the 2011 data? 

A driver convicted of “a failure to use or improper use of signal” had a 96% increased likelihood of a crash.

The SAE study also mentions that they made direct observations of both drivers using signals correctly and failing to use signals when warranted.  They found that drivers who were executing a turn were using signals correctly 75% of the time and failed to use them 25% of the time.  Lane changing presented very different use rates – used 52% of the time and neglected 48% of the time.

The SAE study also asserts that there are roughly two million crashes annually due to this failure to use signals.

Signals are meant to convey a forewarning to other motorists of an intended lane departure or entrance (i.e. turn at intersection, merge, change of lane, etc.).  When signals are not used other drivers have less time to react, and this delay can affect various types of collisions ranging from merging/sideswipe to rear end collisions to head on collisions at intersections.

In a National Transportation Safety Board report, it states; “…if passenger car drivers have a 0.5 second additional warning time, about 60 percent of rear end collisions can be prevented.  An extra second of warning time can prevent about 90 percent of rear-end collisions.”  Using signals in advance of turns or merges gives following vehicles time to react and slow down.  By increasing their following distance, they have time to brake or avoid the vehicle in front. 

SAE’s paper makes the following conclusion:  if we assume that becoming involved in a collision due to the driver’s failure to use a signal is as rare as being struck by lightning, and we use the study’s neglect rates applied to the miles driven in the USA each year, then we could determine that up to 1 Million crashes would be averted if signals were universally used by all drivers.

There is no cost to use signals – they’re standard equipment.  There is a cost of not using signals – moving violations and crashes.   Would you commit to step up your use of turn signals the next time you get behind the wheel?

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