In our series of posts about left turns, we have discussed the various factors that contribute to left turn-related accidents. One common accident that can occur during the course of a left turn is a collision with oncoming traffic. Often times, a collision with oncoming traffic may occur due to a misjudgment of the speed and/or distance of the approaching vehicle. In this post, we will discuss this interesting phenomenon. We will dive into the science of why we may misperceive the speed and distance of traffic, and some helpful things to remember to avoid this mistake.
The Science Behind the Misperception of Speed and Distance
- Peripheral Vision: The Human Field of View
When scanning an intersection for hazards, we often rely on our entire field of view to make informed decisions. However, our peripheral vision is often less accurate than our central field of view. Often times, objects in our periphery appear to be moving more slowly than they actually are. Our periphery is mostly intended to detect changes in light and movement, but is less reliable for accurately judging speed and distance.
- The Impact of Angle of Approach
When a left-turning driver pulls into the intersection prior to making the left turn, oncoming traffic is positioned in front of the driver. Trying to judge the speed and distance of an approaching vehicle is more difficult from a head-on angle because the perceived size of the approaching vehicle Will not change as much. Conversely, when positioned perpendicular to a lane of traffic, the passing vehicles may appear to be moving than they actually are.
- Depth Perception Dilemmas
Our ability to perceive depth relies on both monocular cues (such as perceived size of an object) and binocular cues (the difference in images seen by each eye). Changes or disruptions in these cues can affect a driver’s ability to perceive depth accurately.
These issues of misperception can be exaggerated when drivers are in a rush and make a left turn too hastily. Here are some of the factors that can add to the danger of making a left turn:
- Impaired Judgment in a Rush
When a driver is in a hurry, they may have impaired judgement. For example, it is important to properly asses your surroundings before making any road maneuver. Making these maneuvers too quickly may cause drivers to miss potential hazards. In the case on oncoming traffic, a left-turning driver might not give themselves enough time to judge the speed and distance of oncoming traffic before deciding to turn.
- Reduced Margin for Error
Drivers should always give themselves enough time to brake or otherwise act in case of an unforeseen hazard. Drivers who commit to making their left turn too quickly may find that there is a pedestrian in the crosswalk and may not have enough time to stop. They may also fail to see an oncoming vehicle risking a severe accident.
- Increased Anxiety and Its Effects
Drivers who are rushing may be impaired by the effects of anxiety. Anxiety can lead to tunnel vision and poor judgement, a particularly dangerous combination when in comes to left turns.
Avoiding Misjudgments in Left Turns
Drivers may be happy to know that there are things they can do to avoid misjudging the speed and distance of oncoming vehicles. Here are some of those tips and tricks:
- Take Your Time: The Importance of Patience
Taking a few extra seconds to evaluate the traffic environment and road conditions can make all the difference when it comes to left turn safety. It is important to give yourself enough time to recognize all of the potential hazards in an intersection and to get a more accurate read of oncoming traffic.
- Use Central Vision to Enhance Accuracy
It is important no to rely too much on your less reliable peripheral vision. When given the opportunity, drivers should try and shift their focus from peripheral to central vision. This is especially important when it comes to the perception of movement in oncoming traffic.
- Practice Defensive Driving
Defensive driving is a vitally important safety tip for all aspects of driving. When making a left turn, there are various possible scenarios that may compel the left-turning driver to stop or otherwise avoid a collision. Always be ready to brake if necessary, and assume that there may be hazards in your desired direction.
- Consider Intersection Design
Some intersections have better visibility than others. For example, an intersection may be positioned on a hill, making it impossible to see a long distance down the lane of oncoming traffic. It is important to be able to see enough of the oncoming traffic lane to be able to estimate the speed and distance of oncoming traffic. Drivers should only make left turns at intersections that are safe and have good visibility.
- Turn When Safe: Prioritize Safety Over Impatience
Drivers, especially at intersections without green arrow protection, may feel pressured to make their left turn by the driver behind them. Never proceed with your left turn unless it is absolutely safe to do so. Remember, patience is key and you should not try and split a small gap in oncoming traffic.
Left turns can be deceptively complex maneuvers with multiple variables that could lead to a collision. One of those dangerous factors is the need to judge the speed and distance of oncoming traffic. It is important to know about the way our brains perceive fat-moving objects, and how we can easily misjudge the speed and distance of an oncoming vehicle. With that in mind, leave yourself plenty of space to complete your left turn in a safe and cautious manner.
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