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Case Synopsis

A motorist exiting a rural freeway was struck by a motorist on the intersecting State Route at the top of the exit ramp. At the westbound exit ramp from the Interstate freeway the State Route a stop sign is posted at the end of the ramp requiring exiting traffic to stop before entering the State Route. However, the eastbound off ramp traffic is not required to stop before entering the State Route. A stop sign is posted on southbound State Route at the ramp terminal. This is an unusual traffic signing pattern for interstate off ramps. Expert observations of the operation of this intersection showed that a large proportion of the eastbound off ramp traffic slowed down at the end of the ramp, expecting to stop at the State Route. Southbound State Route traffic, on the other hand, did not necessarily stop for the stop sign. A short observation period tabulated 10% of the southbound traffic which did not stop for the stop sign. The non-compliance with the stop sign is likely related to its unexpected location.

  1. Is the traffic signing consistent with the requirements of the Manual on Uniform Traffic Control Devices (MUTCD)?
  2. Is the traffic signing sufficient to warn motorists of unusual signing at the State Route/Interstate eastbound off ramp intersection?
  3. Did the traffic signing adequately consider Human Factors and driver expectations?
  4. 4. Did the State Department of Transportation fulfill its duty to provide safe roads at this intersection?

Expert Analysis:

At the Interstate interchange, the eastbound off ramp is not required to stop before entering the State Route. A stop sign is posted on southbound State Route at the ramp terminal. This is an unusual traffic signing pattern for interstate off ramps. Expert observations of the operation of this intersection indicated that a large proportion of the eastbound off ramp traffic slowed down at the end of the ramp, expecting to stop. Southbound traffic on the State Route is not expecting to stop at the eastbound Interstate off ramp and Beaubien Engineering observed violations of this stop sign.

Given the pattern of right angle crashes at this intersection, the State Department of Transportation should have provided enhanced warnings to motorists about the unusual traffic control signing at this off ramp.

The traffic signing at the State Route/Interstate eastbound off ramp was not consistent with the requirements of the Manual on Uniform Traffic Control Devices. Motorists approaching the intersection did not have sufficient warning of the unexpected right-of-way assignment at the top of the ramp. Driver expectations were not met by the signing pattern at the top of the eastbound Interstate off ramp.

The State Department of Transportation has a duty to consider all aspects of public safety in making decisions about traffic signing on its public roads. When the signing was changed at the Interstate eastbound off ramp/State Route intersection, not all the aspects of public safety were considered. It is not reasonable to ignore the pattern of right angle crashes at this intersection after the change in signing when deciding whether the intersection is functioning in the interest of public safety. When transportation agencies conclude that they should deviate from standard practice for traffic signing in a case, they should document the reasons for this deviation. In cases involving road design deviations, a request for a design exception is documented, explained, and submitted for Federal Highway Administration approval. Beaubien Engineering found no documentation of the reasons or justification for the unusual signing for this intersection.

Result:

The expert concluded that:

  1. The traffic signing was not consistent with the requirements of the Manual on Uniform Traffic Control Devices (MUTCD).
  2. The traffic signing was not sufficient to warn motorists of unusual signing at the State Route/Interstate eastbound off ramp intersection.
  3. The traffic signing did not adequately consider Human Factors and driver expectations.

This case was settled prior to the trial.


Richard F. Beaubien, PE, PTOE is a Professional Traffic Operations Engineer and Managing Director at Beaubien Engineering. He was previously Transportation Department Head at Hubbell, Roth & Clark, Consulting Engineers for more than 23 years. Mr. Beaubien's employment experience includes 5 years as a highway engineer with the Federal Highway Administration and 14 years as the traffic engineer for the City of Troy, Michigan.

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