Near miss on the highway last night. I averted a high speed T-bone impact by a meter or two as Music from the Hearts of Space played on the radio. Good gravy- I was crashing to space music.  My Cherokee is quite stable in an emergency braking maneuver moving straight forward. But if swerving is required, then vehicle sway begins to couple into the steering. Never thought of this control problem before.

Imagine you are sitting at a stop sign waiting to turn left onto a 4 lane highway. To your left is a deceleration lane for traffic moving left to right.  Now, imagine your line of sight as a line extending from your eyes across your left shoulder and into the distance.  Got that?

Now, imagine a car in the deceleration lane on your left slowing to make a right turn at your intersection. A line can be drawn from your eyes to that car. As the car moves toward you, the line extending from your eyes to that car sweeps clockwise across the landscape. Still with me?

Now consider this.  There exists a third vehicle (me) moving from left to right exactly along your line of sight, but behind and eclipsed by the vehicle in the turn lane. As the turn lane vehicle slows down in preparation for a turn, the third vehicle is at a distance and speed such that it continues to remain along the sight line yet remain eclipsed by the turning vehicle.  As the turning vehicle approaches, it’s angular size increases, obstructing even more space behind it.

That is the condition I was in last night. The perversity of trigonometry allows for a set of velocities and alignments that presents a dynamic obstruction of view to evolve.  If the driver at the stop sign grows impatient and attempts to cross the two lanes of traffic before the vehicle in the turn lane completes the turn, he is doing so on the assumption that the blind space is clear. Last night I was in that blind space while an impatient driver pulled in front of me. 

As the driver pulled out, he saw me and hesitated in my (right) lane, causing me to apply heavy braking and to swerve around his rear and away from oncoming traffic. Fortunately for all of us, he stepped on the gas and got out of the way. With the sway of my vehicle with the maneuvering loads, I was on the verge of a loss of control and may have hit him anyway. 

It is interesting how a steady state cruise along the highway can evolve into a complex set of events in just seconds.  In fact, I had anticipated this problem of visibility as I approached the intersection. I disengaged the cruise control and began to decelerate when I saw that the waiting vehicle could not see me. I now think that my deceleration kept me in the blind spot even longer, aggravating and tightening the coupling of the event.  I was barely able to avoid this failure mode even though I was aware of it.  That is scary.