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SAE J2735-Draft-Rev26 [issued: 09-18-08]
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This is an SAE Motor Vehicle Council draft document of the DSRC committee, subject to change.
3.60 on-board unit: An On-Board Unit (OBU) is a vehicle mounted DSRC device used to transmit and
receive a variety of message traffic to and from other DSRC devices (other OBUs and RSUs). Among the
message types and applications supported by this process are vehicle safety messages, a primary subject of
this standard, used to exchange information on each vehicle's dynamic movements for coordination and
safety.
3.61 operations: One of three modes, or states, of operation known as Registration, Initialization, and
Operations which DSRC systems operate in. In the Operations mode a link has been established, the link
will have an open socket with which it can conduct operations in the same manner as with any other 802.11
communications session. The lower layers will be managing the switching between the Control Channel
and the Service Channel. When the radio has switched to another channel, it would appear to the
application as a temporary loss of communications.
3.62 pedestrian change interval: An interval during which the flashing UPRAISED HAND (symbolizing
DONT WALK) signal indication is displayed, often also called the pedestrian clearance time. During this
interval the SPAT messages indicates a don’t walk state for that pedestrian lane (along with an optional
period of time remaining for this state).
3.63 pedestrian clearance time: The minimum time provided for a pedestrian crossing in a crosswalk,
after leaving the curb or shoulder, to travel to the far side of the traveled way or to a median. During this
interval the SPAT messages indicates a Flashing Don’t Walk indication for that pedestrian lane (along with
an optional period of time remaining for this state). The duration for such time intervals comes from
MUTCD and is based on a rate of speed of 2 meters per second.
3.64 pedestrian phase: The time during which a walking figure or word “WALK” is presented and the
DON’T WALK is presented. The pedestrian phase is also the time interval of the pedestrian walk interval
and the pedestrian change interval combined.
3.65 pedestrian walk interval: An interval during which the WALKING PERSON (symbolizing WALK)
signal indication is displayed. When a verbal message is provided at an accessible pedestrian signal, the
verbal message is “walk sign.” During this interval the SPAT messages indicates a walk state for that
pedestrian lane (along with an optional period of time remaining for this state and the subsequent
pedestrian clearance state).
3.66 permissive mode: A mode (left or right) of traffic control signal operation in which, when a
CIRCULAR GREEN signal indication is displayed, left and/or right turns are permitted to be made after
yielding to pedestrians and/or oncoming traffic.
3.67 preemption control: The transfer of normal operation of a traffic control signal to a special control
mode of operation.
3.68 pretimed operation: A type of traffic control signal operation in which none of the signal phases
function on the basis of actuation. When such a signal operation is reflected in the SPAT message, the time
intervals given for various signal phases are fixed and do not vary based on any form of actuation.
Pretimed operation may be fixed or based on time of day schedules.
3.69 protected mode: A mode (left or right) of traffic control signal operation in which left or right turns
are permitted to be made when a left or right GREEN ARROW signal indication is displayed.
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