Oregon Administrative Rules
Chapter 734 - DEPARTMENT OF TRANSPORTATION, HIGHWAY DIVISION
Division 20 - TRAFFIC CONTROL
Section 734-020-0019 - Locations and Criteria of Variable Interstate Speed Limits
Universal Citation: OR Admin Rules 734-020-0019
Current through Register Vol. 63, No. 3, March 1, 2024
This rule is applicable only to regulatory systems and not to advisory systems.
(1) All locations of interstate highways have maximum speed limits set in section (2) of OAR 734-020-0011 or statutory maximum speed limits per ORS 811.111.
(2) Variable speed limits on the following sections of interstate highways are established as follows:
(a) I-84 Eastbound, MP 277.49 - MP 305.00:
The following sections each may have different speed limits based on the
criteria in section (3) of this rule:
(A) 1.15
mile west of Clover Creek Interchange Structure (MP 277.49) to 0.30 mile east
of North Powder River (MP 286.50).
(B) 0.30 mile east of North Powder River (MP
286.50) to 100 feet west of Culley Lane Structure (MP 295.65).
(C) 100 feet west of Culley Lane Structure
(MP 295.65) to 0.86 mile east of Campbell Street Interchange Structure (MP
305.00).
(b) I-84
Westbound, MP 277.88 - MP 306.40: The following sections each may have
different speed limits based on the criteria in section (3) of this rule:
(A) 0.76 mile west of Clover Creek
Interchange Structure (MP 277.88) to 0.67 mile west of North Powder Interchange
Structure (MP 285.01).
(B) 0.67
mile west of North Powder Interchange Structure (MP 285.01) to 0.24 mile west
of Culley Lane Structure (MP 295.43).
(C) 0.24 mile west of Culley Lane Structure
(MP 295.43) to 0.13 mile west of S. Baker Interchange Structure (MP
306.40).
(c) I-5
Northbound, MP 3.68 - MP 12.00: The following sections each may have different
speed limits based on the criteria in section (3) of this rule:
(A) 0.95 mile south of Siskiyou Highway
U'xing (MP 3.68) to 0.29 mile south of Box Hill Creek (MP 5.97).
(B) 0.29 mile south of Box Hill Creek (MP
5.97) to 0.27 mile south of Neil Creek Road U'xing (MP 10.08).
(C) 0.27 mile south of Neil Creek Road U'xing
(MP 10.08) to 0.16 mile north of Clayton Creek (MP 12.00).
(3) Criteria for Changing Speeds. The Variable Speed Limit system has two automated subsystems, 1) a congestion subsystem and 2) a weather subsystem, each determining a recommended speed based on criteria set forth below in (a) and (b). The system also includes a manual control subsystem with criteria for use as described below in (c). The system automatically displays the lowest recommended speed from the automated subsystems with the ability for limited manual intervention when appropriate.
(a) Automated variable speed limits for
congestion:
(A) During periods of free flow or
near free flow when there is little or no congestion and drivers are not
impeded by other vehicles, the subsystem will be programmed to select the
maximum speed limit.
(B) During
periods of congestion characterized by slower speeds on the roadway the
subsystem will be programmed to select recommended reduced speeds corresponding
to the congested conditions.
(C)
The 85th percentile speed will be calculated from traffic sensor data. The
variable posted speed limit shall be the 85th percentile speed rounded to
within 5 mph. If there are multiple traffic sensors within the segment, the
85th percentile speed will be taken from the speed sensor with the lowest
speed.
(D) If the subsystem does
not have sufficient data to calculate the 85th percentile speeds, occupancy
data (percent of time a vehicle was on the sensor) shall be used to determine
if vehicles are stopped at the sensors. If the presence of vehicles is
indicated, then the subsystem will assume traffic is stopped and display the
minimum speed limit.
(E) If the
subsystem is unable to determine a recommended speed due to the lack of data,
the subsystem will use the last valid speed until a new speed is
calculated.
(b)
Automated variable speed limits for adverse weather conditions:
(A) The weather responsive subsystem will
select recommended reduced speeds during periods where speeds are required to
be at least 10 mph below the maximum speed limit due to either adverse weather
conditions or other safety hazards.
(B) Weather sensors must be installed within
the corridor. These sensors may measure such elements as the friction of the
roadway (grip factor), classify roadway surface conditions (ice or snow
present), measure visibility, or other factors related to weather depending on
the corridor and reoccurring conditions.
(C) The variable speed determined by weather
sensor data shall generally be 10 to 20 mph lower than maximum speed limit in
the segment depending on severity and number of conditions present. If the
maximum speed limits on the highways are above 65 mph (i.e., speeds on
interstate are 70 or 75 mph) then the variable speeds shall be lowered to 55
mph and 45 mph depending on severity and number of conditions present. The
minimum speed limit of 30 mph will be reserved for the most severe weather
conditions in combination with low visibility or where significant traction
problems are present.
(D) The TOC
has authority to disable the weather responsive subsystem when necessary or
override the speed if other conditions are present and not being detected by
weather sensors.
(E) The subsystem
shall also consider the snow zone chain condition in place during inclement
weather conditions. ODOT establishes the chain conditions based on OAR
734-017-0005 thru 0025.
(i) When chains are
required on some classes of vehicles, but not all, the subsystem will recommend
a 45 mph speed.
(ii) When chains
are required on all vehicles the subsystem will recommend a 35 mph
speed.
(F) When a chain
condition is present and a weather event is being detected the slowest
recommended speed shall be used.
(c) When sensors are not detecting properly
or conditions are such that the automated system does not adequately address
the conditions present on the roadway the TOC may establish variable speed
limits other than those established by either the weather subsystem or the
congestion subsystem in accordance with the following:
(A) The TOC shall have the ability to
temporarily override the system when in the judgement of the Department it is
necessary to protect the safety of the public or workers, or avoid damage to
any portion of the highway.
(B) Key
information such as weather and displayed speeds from the automated systems, if
available, should be used to provide information for decision making.
(C) The minimum period for changing speeds
may be overridden by the TOC and the posted speed changed
immediately.
(D) Unforeseen
conditions not covered by the automated system may necessitate overriding the
automated system such as a major natural disaster or evacuation.
(E) Other conditions include setting the
variable speed system to a lower speed for properly documented reduced speeds.
Examples include construction work zones or emergency conditions such as
landslides.
(F) When manual control
is requested, the TOC shall record who made the request and the reason for the
request.
(d) General
conditions for variable speed limits:
(A)
Speed signs shall not display a speed greater than the designated speed limit
for the segment as set in OAR 734-020-0011 and if none, then the statutory
maximum speed limit in ORS
811.111.
(B) Speed Limits displayed shall be the
lowest of the two automated subsystems, congestion or weather, unless
overridden by the TOC.
(C) Speed
limits between subsequent highway speed change segments typically shall not be
reduced by more than 10 to 15 MPH between adjacent segments. These may be urban
situations where speed signs are separated by no more than a few miles. In some
cases (such as rural locations) where there are relatively long distances
between speed signs, the speed change between subsequent sections may be much
greater since there may be free flow speeds in adjacent segments and thus no
reason for reduced speeds.
(D) The
speed limit shall be displayed in 5 MPH increments.
(E) The speed limit shall not be decreased
more than once within a 2 minute period, unless overridden by the
TOC.
(F) The speed limit shall not
be increased more than once within a 3 minute period, unless overridden by the
TOC.
(G) The minimum variable speed
limit shall not be less than 30 MPH.
(H) Variable speed signs should be posted
near, and downstream of interstate entrances, typically within about 1500 to
2000 feet.
(I) Variable speed signs
for urban areas should be placed at frequent intervals. For rural areas the
sign interval should be at least every five miles but no more than every ten
miles.
(J) The TOC shall log the
speed limit being displayed on the variable speed signs and keep the log for a
minimum of five years.
(K) Static
signs giving warning of entering the variable speed corridor shall be placed at
the beginning of the corridor.
(L)
Static signs giving notice of the end of the variable speed limit may be placed
at the exit points. A static speed sign shall be placed at the end of the
corridor to establish the end of the variable speed and the beginning of the
fixed speed limit.
Tables referenced are not included in rule text. Click here for PDF copy of table(s)
Statutory/Other Authority: ORS 184.619, 810.180 & 811.111
Statutes/Other Implemented: ORS 810.180 & 811.111
Disclaimer: These regulations may not be the most recent version. Oregon may have more current or accurate information. We make no warranties or guarantees about the accuracy, completeness, or adequacy of the information contained on this site or the information linked to on the state site. Please check official sources.
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