18 Month Study Report on
65 MPH Speed Limit in New Jersey
In 1995, the United States Congress repealed the National Maximum Speed Limit of 55 MPH (in effect since 1974 when it was started as a fuel-saving
measure) and returned to the states the responsibility for setting speed limits on major highways. While Congress allowed states to increase speed
limits on rural interstates to 65 MPH in 1987, New Jersey did not change the 55 MPH speed limit, as very little mileage qualified as rural interstate.
The federal government lifted the rural interstate restrictions in 1995.
In late 1997, the New Jersey Legislature acted to raise the 55
MPH speed limit to 65 MPH on portions of the state highway system,
including but not limited to, interstate highways and highways of
similar design and access control. The legislation also established
the 65 MPH speed limit as prima facie on the New Jersey Turnpike,
the Garden State Parkway and the Atlantic City Expressway. Through
negotiations, the Legislature and the Administration agreed to an
18-month Study test period on "approximately 400 miles" of
highway statewide. The new law, approved January 19, 1998, gave the
Department of Transportation (DOT), in consultation with the
Attorney General and the toll authorities, four months to establish
the designated network, and the DOT the lead in implementing the 65
MPH Speed Limit for the 18-month Study period. The list of these
designated roadway segments is detailed in Appendix A.
An integral enforcement aspect of the new law was inclusion of
safety-related traffic offenses, such as reckless driving, changing
lanes without signaling, and speeding at 10 miles per hour or more
over the 65 MPH limit, for which the fines were doubled if committed
in the 65 MPH zone. The list included what are often characterized
as aggressive driving offenses. Fines were also doubled for offenses
committed while speeding at 20 miles per hour or more in the non-65
MPH zones. While the maximum speed limit was increased, a more
stringent enforcement regimen was established to deter excessive
speed and other unsafe driving practices.
On May 19, 1998, the Commissioner of Transportation designated
475.49 miles of roadway for a 65 MPH Speed Limit in New Jersey,
pursuant to Public Law 1997, Chapter 415, for a study period of 18
months. At the end of this study period, the Department of
Transportation, through a statewide task force, had three months to
submit a study to the Governor and the Legislature. The legislation
provides that the Commissioner of Transportation, in consultation
with the Attorney General and the New Jersey Turnpike Authority (NJTA),
the New Jersey Highway Authority (NJHA), and the South Jersey
Transportation Authority (SJTA), shall recommend speed limit
modifications, and whether 65 MPH roadway mileage should be
increased, decreased or stay the same.
During the 18-month study period following implementation of the
65 MPH, the statewide task force (consisting of representatives from
NJDOT, NJTPA, NJHA, SJTA and the New Jersey State Police) looked at
overall impacts on factors such as public safety, environmental and
cost issues, speed, accident rates, fatalities, enforcement, and air
II. Initiation of New Maximum Speed Limit
A. Establishment of Task Force
A Task Force was established of representatives within the DOT to
develop an Implementation Plan, and an 18-month Study Plan.
Representatives include the following divisions/bureaus: Traffic
Engineering and Safety Programs, Operations, Capital Program
Management/Design Services, Division of Transportation Systems
Planning, Transportation Data Development, Legislative Analysis,
Motor Vehicles, Communications and Deputy Attorney General for DOT.
Representatives of other non-DOT agencies include: Toll Authorities,
State Police, Highway Safety, Attorney General, and Administrative
Office of the Courts. The Task Force met throughout the study
B. Selection of Roadways for 65 MPH
To determine the approximately 400 miles of roadway segments to
be posted at 65 MPH, the Task Force used criteria that would help
identify for the public the different environments between 55 MPH
and 65 MPH. The roadway segments selected for 65 MPH were based on
the following criteria:
C. Initiation of 65 MPH Speed Limit
Segments must be at least 10 miles in length - This is an
informal national standard intended to prevent driver confusion
from seeing too much variance in posted speed limits on the same
roadway. This eliminates the short freeway segments on State
Routes including: Rtes 1, 3, 4, 15, 21, 24, 29, 33, 42, 440, and
Spacing of access ramps must not be too short - When there
are closely spaced ramps, it leads to significant roadside friction,
with all the weaving and merging movements occurring, making travel
at higher speeds less safe. This tends to be common in the inner
Roadway Segment must be designed for 65 MPH - This tends to
be a problem in the inner urban areas with significant developments
and high population densities. In order to accommodate the heavier
traffic volumes, design characteristics of the roadway may not be
favorable to higher speeds. These design characteristics include
acceleration and deceleration lanes to and from low speed ramps,
vertical curves crossing over surface streets, narrow shoulder
widths, etc. Again this tends to be most common in the inner urban
Roadway Segment must not experience significant recurring
congestion - Roads that experience significant congestion over
several hours of the day, create an environment that can be unsafe
for higher speeds. Although these roads may experience light traffic
at late night and early morning hours, the periods of congestion
experience significant weaving and higher numbers of accidents.
In summary, the roadway segments selected for the 65 MPH Speed
Limit tended to be in rural and suburban settings, while the 55 MPH
Speed Limit remained in the more urban areas.
The Task Force identified necessary signing and safety measures
to implement the 65 MPH speed limit. Where appropriate, this
included change of 55 MPH Speed Limit signs to 65 MPH speed limit
signs, installation of AReduce
Speed Ahead@ signs at the
end of the 65 mph zones, and "fines doubled@
signs at intermittent points along the 65 MPH zones.
An 18-month Study Plan was developed to assess impacts to travel
speeds, safety records, enforcement, and the environment (air and
noise). This required taking field measurements and accumulating
data from agency record-keeping systems.
Due to the change in the fine schedule, efforts to develop, print
and distribute fine schedules through the Administrative Office of
the Courts for new police summons were expedited prior to initiation
of the 65 MPH speed limit.
To make comparisons of the 55 and 65 MPH speed limits, a
compilation of Abefore@
data was required for the Study Plan by the Task Force.
When the 65 MPH speed limit began on May 19th, all these
requirements were completed and in place.
Travel speeds were measured at least once every three months at
various points along New Jersey highways posted at 65 MPH and 55 MPH
through the use of detector stations. The type of detector station
used on the state highways is an in-ground inductive loop detector
that measures the speed of each vehicle which passes over the
detection zone. This data is collected and processed to analyze the
travel speeds and volumes. Attached is a Monitoring Report of
measurements made on the state highways. At various locations, Abefore@
measurements were taken prior to May 19, 1998 (when 65 MPH went into
effect), with Aafter@
measurements taken and presented for comparison. The volume of
vehicles for each 24-hour period is presented. Then, travel speeds
are presented in terms of Aaverage@
Average speed is the most commonly used speed statistic and
is the summation of all individual speed measurements divided by the
total number of vehicles.
The last three columns of the tables in Appendix B reflect the
percentage of motorists exceeding 65 MPH, 70 MPH and 75 MPH.
Median speed is the speed which is exceeded or equaled by
exactly half the vehicles from which the data was collected.
85th-percentile speed is sometimes referred to as the
critical speed as it is commonly used as a guide in establishing
reasonable speed limits. This represents the speed which 85% of the
vehicles are traveling under.
Environmental impacts were measured by the DOT for both air and
noise levels. Air quality and noise level measurements were made by
models, based on field measurements of travel speeds and volumes.
Actual field measurements would not be useful as they would be
subject to undetermined factors influencing readings.
Throughout the study period, the State Police collected data on
accidents and violations.
A. Travel Speeds
Changes in the measured average travel speeds in the 65 MPH zones
were found to experience nominal differences compared to prior 65
MPH conditions, as some locations increased and some decreased,
generally less than 2 mph. Appendix B identifies the travel speeds
taken at various time intervals for different sections of the state
The only difference to this similarity appears on the New Jersey
Turnpike, where the Abefore@
travel speeds are within 3-4 mph. The "after" speeds on
the Turnpike are comparable to the other highways in the study.
There were different measuring techniques between the DOT and the
three toll authorities, however, the measuring techniques used were
consistent during the Abefore@
time periods. Appendix C contains the speed surveys from the toll
In conclusion, the reasons for the nominal differences in the
travel speeds could be due to many factors, including enforcement,
public outreach, respect for the speed limit, uniformity in traffic
flows, and increased fines. The change to the 65 MPH speed limit
during the study period had minimal impact on actual travel speeds.
B. Environmental Impacts
Environmental impacts were studied by the DOT for both air and
noise levels. Air quality and noise levels were determined by models
based on field measurements of travel speeds and volumes. Increases
in speed tend to mean increases in emissions, however, changes in
routes by motorists could affect the emissions too.
In order to estimate the impact on air quality, the analysis was
conducted to investigate potential travel speed changes and traffic
diversions to the higher-speed facilities. Because the speed limit
change affected facilities throughout New Jersey, the New Jersey
Statewide Model was utilized. In order to estimate the change in
emissions resulting from the higher-speed facilities, speeds for the
modeled traffic volumes were calculated using the network Post
Processor for Air Quality (PPAQ). Emission estimates were calculated
within PPAQ using the MOBILES emission program developed by the US
The air quality study was conducted based upon a set of observed
speed and volume data collected over the 18-month study period. The
emissions were calculated for the "before@
condition using data collected prior to the speed limit increase and
the "after@ condition
using data collected after the increase. The results of these
conditions were compared to determine air quality impacts.
Changes in travel speed can potentially affect many aspects
related to travel, which in turn could affect the rate of emissions.
The observed data indicate that the speed changes on most of the 65
MPH facilities increased an average of one mph, except for some of
the Turnpike facilities which increased by an average of four mph.
Therefore, the speed changes from the observed data are reflected in
the air quality analysis.
Another aspect is the potential for traffic diversion to the
higher speed facilities, as the increased speed would provide
potential travel timesavings over the nearby parallel routes.
However, the small amount of traffic diversion observed directly
from the data was inconclusive. The changes reflected are within the
margins of error associated with the data collection equipment and
Considering that the observed aggregate speed changes listed
above and that the levels of potential diversion for the increased
speed are relatively minor, the emission analysis assumed that
diversion would not be significant. The air emission analysis
indicated nominal increases of 0.20%, 0.90%, and 1.15% for Volatile
Organic Compounds (VOC), Nitrous Oxides (NOx), and Carbon
Monoxides (CO) emissions, respectively.
It is generally accepted that it requires a change in noise level
of 3 decibels or more to be perceived by the general public. The
change in travel speeds reported in this study are at most 2 mph.
This small change in travel speed would not generate an increase in
noise levels of 3 decibels and therefore would not be a perceptible
change in the noise environment adjacent to the highways.
Fatal accidents in 65 MPH zones have decreased since the
implementation of the 65 MPH speed limit. There were ten fewer
deaths, representing a 9.6 percent decrease, on the sections of
highway that now have the 65 MPH speed limit and seven fewer fatal
accidents, representing a 7.9 percent decrease, than on those
sections of highway for a comparable time period. It should be
noted, however, that fatal accidents comprise less than one percent
of all reported accidents and may not be a statistically relevant
indicator of safety.
Notably, accidents on sections of highways with 65 MPH speed
limits increased 18.3 percent. Accidents with injuries increased by
9.4 percent, and the total number of people injured increased by 5.9
percent from a comparable time period. An analysis of certain 65 MPH
zones and adjacent 55 MPH zones were made for comparison basis with
accidents from the 12-month period before 65 MPH was implemented, to
the 12-month period after 65 MPH was implemented. The highways
analyzed were I-78, I-80 and I-287. The findings showed that
accidents increased in the 65 MPH zones by 12.0%, and increased in
the 55 MPH zones by 12.9%.
Accident rates fluctuate over time. In periods between 1984 and
1996, rates vary as much as 12 percent per year. The study captured
data for a fixed 18-month period. Accordingly, it is not possible to
determine whether the increase in accidents in 65 MPH zones
represents a normal fluctuation in accident rates or suggests that
increased speed contributes to increased accidents. Appendix D
identifies overall fatal accidents and total accidents in 65 MPH
roadway segments and individually for each roadway segment selected
for the test period.
Appendix F provides information on State Police enforcement
efforts since implementation of the 65 MPH speed limit. The table
summarizes the number of speeding summons (broken down incrementally
by the number of miles over the speed limit), accident data (broken
down by accident type), and "aggressive driver" violations
(broken down by specific statutory violations). The enhanced speed
enforcement campaign of the State Police resulted in approximately
one-third of all speeding summons being issued for speeding 1-9
miles over the posted speed limit.
The following summarizes the findings of the 18-month study
Some roadway sections in the 65 MPH zones appear to be very
favorable for the 65 MPH speed limit; however, with other roadways,
the information is mixed. The data is not conclusive. Therefore, it
is recommended that any conclusive long-term decisions on the 65 MPH
speed limit cannot be made at this time. Rather, it is recommended
to extend the study period another 18 months, in order to perform a
more detailed analysis that is completed in a time frame more
acceptable for professional practice in the area of transportation
Average increase in travel speeds of 1 mph, on the various
roadway sections in the 65 MPH zones, with the exception of the
Turnpike which increased 3-4 mph, on various segments. The
"after" speeds on the Turnpike ranged from 63 to 68 MPH,
falling in line with the "after" speeds on the other
Environmental impacts regarding air quality and noise were only
nominally affected due to the nominal change in the travel speeds.
Fatalities decreased 9.6% and fatal accidents decreased 7.9% in
the 65 MPH zones over a similar 18-month period prior to the study
Reported accidents increased 18.3% in the 65 MPH zones over a
similar 18-month period prior to the study period. Adjacent 55 MPH
zones had slightly higher increases in the number of reported
accidents than the 65 MPH zones during a similar time period.
As noted previously, accident rates fluctuate over time. In
periods between 1984 and 1996, rates vary as much as 12 percent per
year. The study captured data for a fixed 18-month period.
Accordingly, it is not possible to determine whether the increase in
accidents in 65 MPH zones represents a normal fluctuation in
accident rates or suggests that increased speed contributes to
The Department of Transportation, in consultation with the
Attorney General, the New Jersey Turnpike Authority, the New Jersey
Highway Authority, and the South Jersey Transportation Authority,
recommends that the existing roadway segments currently posted at 65
MPH be maintained at 65 MPH, and that no additional mileage be added
at this time.
Monitoring by all agencies on the Task Force should continue with
reports on the maximum speed limit, submitted to the Commissioner of
Transportation. Furthermore, staff should take a closer look at any
locations experiencing higher frequencies of accidents. At this
point, it is not known why accidents increased, and it raises great
concern. However, the Task Force needs to learn more about the
increases and implement appropriate safety counter-measures at
appropriate locations, along with a proactive outreach to educate
motorists on safe travel. An increase in the size and scope of the
study is warranted. Further, analysis is needed on parallel and
adjacent roadways to better understand the overall effects.
Continue on to Appendix