ITE Journal - May 2020 - 44

Eastbound Hamilton experienced a steep speed decrease
one year after sign deployment. Westbound Hamilton Avenue
experienced both decreases and increases in mean speed with speed
increases three and five years after sign deployment. Civic Center
Drive consistently showed speed decreases in each of the "after"
surveys. At best, the speed changes on multi-lane arterials may be
described as mixed and inconclusive.
Overall, speed change percentage differences for each of the
surveyed streets are statistically significant. In terms of absolute
speed changes in miles per hour, speeds did not change markedly.
The maximum change for any sign location was a one mph increase
or decrease.
Based on street classification, all local streets experienced speed
change decreases and only one collector experienced a speed change
increase after five years. The local and collector streets are all 40 ft.
(12 m) wide, two-lane streets with on-street parking and sidewalks
where the detectors reflect speeds of only one approach lane of
traffic; the source for the vehicle speed being displayed is clear.
The sign facing Westbound Hamilton Avenue displays speeds
for three lanes of approaching traffic; motorists may be less clear on
whose speed is being displayed. The radar sign may be outside of the
cone of vision of motorists who are traveling in the lanes furthest
from the sign.

sign deployment. And though the speed changes are statistically
significant, to the average member of the public a speed change of
one mph may be perceived as immaterial. It is therefore a matter of
public policy to determine if the magnitude of speed change shown
is of sufficient importance to warrant the deployment of radar speed
feedback signs.
Finally, whereas the scope of this study focuses on the effectiveness of radar speed feedback signs on speed reduction over time,
the authors acknowledge that the relationship between speed and
crash risk should be studied to determine whether speed reductions
resulting from the deployment of radar speed feedback signs
translate into quantified reductions in injury crashes. itej

Conclusion and Recommendations for
Additional Research

1.	 A.E. (Tony) Churchill and Surendra Mishra. "Speed feedback signs as a
tool to manage demand for lower residential speeds." Transportation
Association of Canada. 2016. https://www.tac-atc.ca/sites/default/files/
conf_papers/churchill.pdf [Accessed October 3, 2019].
2.	 Hildebrand, E. D., Mason, D. D., Paradis, D. P. and Hazard, K. E. "Long
Term Effectiveness of Radar Speed Display Boards Used in School
Zones." Proceedings of the 24th Canadian Multidisciplinary Road Safety
Conference, Vancouver, BC, June 1-4, 2014.
3.	 Veneziano, D., Hayden, L. and Ye, J. "Effective Deployment of Radar Speed
Signs." A Project Conducted Under California and Oregon Advanced
Transportation Systems (COATS) Phase IV Final Report. 2010.

The results of this study indicate that continuous use of radar
speed feedback signs provides prolonged speed management where
applied. The use of radar speed feedback signs resulted in mean
speed changes that were statistically significant five years after sign
deployment. Streets that experienced the greatest speed reductions
were 40 ft. (12 m.) wide, two-lane local streets with on-street
parking on both sides. The three segments (eastbound McCoy
Avenue and both directions of Victor Avenue) that experienced
consistently decreased speeds had schools located along the street.
Perhaps motorists traveling on these street segments feel obligated
to slow down near schools. Based on the data, perhaps the best
results for decreasing speeds occur when radar signs are installed
on local streets with one-lane approaches and signs are within a
motorist's cone of vision.
Speed changes on surveyed multi-lane arterials varied. One
street segment experienced both speed decreases and increases
over time with the last two time periods showing speed increases.
It is questionable whether signs are effective on wider streets with
multiple approach lanes of traffic.
Overall, speed decreases were lower than observed in other
studies. This distinction may reflect the short-term nature of
previous studies except for Hildebrand et al.2 The other studies
appeared to include data that were collected within 12 months of
44

May 2020

i te j o urnal

Acknowledgements
Thanks to Doris Quai Hoi and Srilakshmi Sakhamuri for
downloading the data used in this study and David Mooso and
Armando Herrera for maintaining the radar speed feedback signs
on behalf of the City of Campbell.
The contents of this paper reflect the views of the authors, who
are solely responsible as individuals for the accuracy of the facts and
conclusions presented herein. These views do not necessarily reflect
those of the City of Campbell.

References

Matthew J. Jue, P.E., PTOE (M) is the city traffic
engineer for the City of Campbell in CA, USA. He
received a B.S. and M.S. in civil engineering from San
Jose State University and a M.S. in transportation
management from the Mineta Transportation Institute
of San Jose State University.
James T. Jarzab is the principal for Commuter
Associates. He holds both bachelors and masters degrees
in economics from Bradley University and Illinois State
University, respectively. He has extensive managerial
experience in public transportation.


https://www.tac-atc.ca/sites/default/files/conf_papers/churchill.pdf https://www.tac-atc.ca/sites/default/files/conf_papers/churchill.pdf

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