September 16, 1998
To:Etobicoke Community Council
From:D. Gulli, Director, Transportation and Engineering Planning
Subject:Speed Limit Compliance on Urban Streets
Purpose:
Regarding a submission from a Ms. R. Swarbrick on the subject of speed compliance on
urban streets.
Financial Implications:
There are no funding implications associated with this report.
Recommendation:
It is recommended that this report be received.
Background:
At its meeting of May 6, 1998, Etobicoke Community Council received correspondence
dated from Ms.R.Swarbrick of Prince Edward Drive (Attachment No. 1). In her
correspondence, Ms. Swarbrick made reference to a number of issues, particularly the
following:
-the results of RADAR speed surveys in certain areas of the community; and
-vehicle operating speeds in excess of posted speed limits that are not considered to be
within the enforceable range.
Community Council requested that staff review and report on Ms. Swarbrick's submission.
Discussion:
There are two fundamental issues raised in Ms. Swarbrick's correspondence. They relate to
the operating speed of a roadway, and police enforcement of the posted speed limit. To
address these two issues, this report briefly describes the difference between posted speed
and operating speed, and how the posted speed of a roadway is determined. The latter part of
this report addresses operating speed, and the related issue of police enforcement.
Posted Speed
The selection of posted speed is essentially a traffic operation consideration that is strongly
influenced by the road's design speed. Design speed is selected for the purpose of functional
design, and is typically considered to be ". . . the highest continuous speed at which
individual vehicles can travel with safety on a road when weather conditions are so
favourable and traffic density is so low that the safe speed is determined by the geometric
features of the road." The posted speed is often set at 10 km/h less than the design speed;
however, unlike the posted speed, the design speed is a function of a road's geometry and
cannot be changed without reconstruction .
Legislation contained in Part IX, Section 128(1)(b) of the Highway Traffic Act states that:
"No person shall drive a motor vehicle at a rate of speed greater than, . . . 50 kilometers per
hour on a highway within a city, town, village, police village or built-up area." The Act
allows municipal council to ". . . prescribe a rate of speed different from the rate set out in
subsection (1)" for roads under its jurisdiction, and this revised speed limit is usually
determined on the basis of traffic engineering studies.
Operating Speed
Speed studies focus on the velocity of vehicles passing a point on a roadway under free-flow
conditions. These studies provide information on driver behavior and the driver's perception
of an appropriate operating speed that is based on existing weather conditions, available
sight distances, traffic density, road alignment and surface treatment.
Typically, the automatic method is utilized to conduct speed surveys. There are two types of
automatic equipment used in speed surveys: road detector meters; and RADAR meters.
Road detectors collect data from detectors located on or within the pavement. Impulses,
either pneumatic or electronic, are transmitted to a unit that records the time of passage
between two detectors spaced a known distance apart. RADAR is employed by mounting a
RADAR unit inside an unmarked vehicle, and recording the speed of each vehicle.
Percentile speeds are used to statistically describe vehicle speeds. A percentile speed is the
speed below which the stated percent of vehicles in the traffic stream travel; e.g., an
85th-percentile speed means that 85per cent of the vehicles in the traffic stream travel at or
below this speed.
Since the 1930s, it has been an accepted practice for traffic engineers to analyze individual
vehicle operating speeds to establish speed limits in the 70 to 90 percentile range, with the
most common accepted value being the 85th-percentile. The 70 to 90 percentile range is
normally used because it has long been recognized that artificially low posted speed limits
are ignored, divert law enforcement resources from other, more important duties, and simply
results in ticketing motorists who were already driving at safe operating speeds. Research
also shows that vehicle speeds typically return to normal two days after police enforcement
has been removed.
Prince Edward Drive Speed Case Study
The existing speed limit on Prince Edward Drive is 40 km/h. This Department's RADAR
speed survey found an 85th-percentile speed of 49.74 km/h along Prince Edward Drive,
south of King Georges Road, and 46.29km/h for the segment of Prince Edward Drive, south
of Queen Anne Road. While these 85th-percentile speeds were 10 km/h above the posted
limit, based on the existing road characteristics of this section of Prince Edward Drive; i.e.,
level terrain combined with good vehicle sight distances and a linear alignment, they were
acceptable, and safe, operating speeds. This being the case, there appears little to be gained
by aggressively enforcing the posted limit, since only a minority of the vehicles traveling on
this section of roadway can be considered as operating at an unsafe speed, or within a speed
range that cannot be effectively controlled through periodic police enforcement.
Conclusions:
The 85th-percentile speeds recorded on Prince Edward Drive reflect a reasonable, safe
operating speed for prevailing road and vehicle traffic conditions. Beyond occasional police
presence, there is little to be gained from an aggressive program of speed enforcement along
Prince Edward Drive.
Contact Name:
Richard Pernicky, Transportation Technologist -Transportation and Engineering Planning.
(416)394-8415; Fax (416)394-8942.
D. Gulli
Director, Transportation and Engineering Planning
cc:Street File: Prince Edward Drive
