Speed Limit–Related Issues on Gravel Roads
Litao Liu
Department of Civil Engineering
Kansas State University
2118 Fiedler Hall
Manhattan, KS 66506-5000
[email protected]
Sunanda Dissanayake
Department of Civil Engineering
Kansas State University
2118 Fiedler Hall
Manhattan, KS 66506-5000
[email protected]
ABSTRACT
Speed limits on gravel roads in Kansas are regulated at 55 mph, as per the Kansas Statutes. In some
instances, this regulatory speed limit has been altered on some gravel roads in several counties. These
changes were expected to provide a safer driving and living environment for gravel road users and rural
residents. However, the effectiveness of such changes still needs to be evaluated so that future
recommendations can be made as feasible as possible. With the lack of detailed literature on this subject,
studies need to be developed to find out whether the 55 mph speed limit is appropriate for current
conditions on gravel roads.
The methodology in this study is built upon three facets. The first is field studies that were performed at a
number of locations on gravel roads. Actual speed data were analyzed to obtain percentile speeds and
other relevant measures based on different categories of roads and weather conditions. The second part is
a questionnaire survey, which was performed to solicit opinions from county road agencies. A list of road
characteristics was rated by respondents to determine how important these characteristics would be in
setting speed limits on gravel roads. The third part involved a statistical analysis of crash data related to
gravel roads in Kansas during recent years. Most variables were found to be significantly interrelated with
speed limits and had an impact on crash severity. The findings of this research are useful for county
engineers for understanding the nature of speed limit–related issues on gravel roads.
Key words: gravel roads—rural roads—speed limit
Proceedings of the 2007 Mid-Continent Transportation Research Symposium, Ames, Iowa, August 2007. © 2007 by Iowa State
University. The contents of this paper reflect the views of the author(s), who are responsible for the facts and accuracy of the
information presented herein.
INTRODUCTION
There are over 1.4 million miles of unpaved roads in the United States, which accounts for 35.3% of the
total road network and carries around 12.4% of the total annual vehicle miles traveled (FHWA 2005). In
2005, a total of 39,189 fatal crashes occurred and 43,443 people died in traffic crashes in the United
States; 536 fatal crashes occurred on gravel roads (1.4% of total), and as a result 594 persons died (1.4%
of total) (USDOT 2007). In the state of Kansas, there are over 98,000 miles of gravel roads, accounting
for about 72.5% of the total state mileage, which is a notable proportion compared to the national average
(FHWA 2005). In the year 2005, there were 384 fatal crashes on all types of roads in Kansas, 35 of which
(9.1%) occurred on gravel roads, which was more than six times the national level (1.4%). In Kansas,
altogether 428 people died as a result of motor vehicle crashes, and 38 (8.9%) of those died on gravel
roads, which was also a significant percent compared to the national level (USDOT 2007).
In the highway classification used by the Kansas Department of Transportation (KDOT), five classes (A
through E) are classified. Gravel roads fall into the fifth class, “E,” and are classified as “E-2” by their
surface type, which is considered inferior to paved roads (H-2) and bituminous roads (G-1) and superior
to graded and drained roads (C), unimproved roads (B), and primitive roads (A) (Russell et al. 1996). A
55 mph blanket speed limit (BSL) was implemented for all gravel roads by the Kansas Statutes, and some
lower speed limits were regulated on a number of special sections as needed. In 28 states, 55 mph is
accepted as a regulatory speed limit for gravel roads (USDOT 2001). Table 1 lists those states that use a
different BSL than 55 mph on gravel roads.
Table 1. List of the states using a different BSL from 55 mph on gravel roads
BSL
States
35 mph
Alabama, Georgia, and Virginia
40 mph
Massachusetts, South Carolina
45 mph
Maine
50 mph
Delaware, Iowa (between sunset and sunrise), Maryland, Nebraska, Rhode Island
(45mph during the nighttime), Vermont, and Washington
60 mph
Arkansas (50 mph for trucks), Texas (55 mph during the nighttime)
65 mph
Alaska, Arizona, Minnesota (during the daytime), Mississippi (55mph for trucks
or truck-trailers), Tennessee, Wyoming
70 mph
Montana (65 mph during the nighttime)
75 mph
Nevada, New Mexico
Source: USDOT, National Highway Traffic Safety Administration, 2001.
Improvement of traffic safety on gravel roads is a concern of many county engineers. The effectiveness of
using the blanket speed limit vs. speed zones needs to be studied. The objective of this study is to find out
how the 55 mph BSL is being complied with by road users, how county engineers think about speed
limit–related issues on gravel roads, and how speed limit is related to crash severity on gravel roads.
METHODOLOGY
Three steps were carried out in this study:
1. Field speed study
2. Questionnaire survey
3. Crash analysis
Liu, Dissanayake
2
First, vehicle speeds were observed and recorded in special traffic counting devices, and then the data
were analyzed to obtain important percentile speeds and speed distributions according to weather and
road conditions. Second, a survey was administered to around 105 counties in Kansas to collect opinions
and comments from county engineers. Third, the Kansas Accident Recording System (KARS) was used
to perform a statistical analysis of crashes on gravel roads. The contingency table test method was used to
analyze the crashes during the 2003–2005 time period, with the expectation of finding out whether speed
limits have an impact on the severity of crashes on gravel roads.
FIELD SPEED STUDY
The speed studies were conducted on gravel roads in Riley County, Kansas. The county map categorizes
gravel roads into county roads and township roads. County roads are graded and maintained by
contractors of the Riley County Highway Department, and township roads are maintained by township
road personnel. County roads were observed to have wider roadways, better graded surfaces, and drainage
than township roads.
Speed Data Collection
The principle in selecting study sites was that the sites should be under general conditions and distant
enough from special sections like curves, bridges, or intersections, because speeds are easily influenced
by external environments that cause drivers to change their speeds to keep safe. The speed study was
performed on 21 locations, 10 of which are on county roads and the other 11 of which are on township
roads. Figure 1 shows the road locations studied.
Figure 1. Field speed study locations in Riley County, KS
Liu, Dissanayake
3
Two sets of traffic counters were used for speed data collection. Each set consisted of a traffic counter,
two road tubes, and accessories, as shown in Figure 2. When an axle passes over the tubes, the air pulses
are conveyed into the counter and two time stamps are recorded as raw data. The spacing of the two tubes
was eight feet. The raw stamp time data was analyzed with specific analysis software provided by the
traffic counter manufacturer. Speed information, together with other data like volume and average daily
traffic (ADT), was turned out in the output. The counting devices worked quite successfully on gravel
roads, especially on very low-volume roads, since the devices can work in the field for a long period
without attendance. The collections were performed at least one week at each location. This was due to
the consideration that weekdays might have different ADT, speeds, and vehicle classifications than
weekends. Sometimes data collection was interrupted by large vehicles, especially farm equipment, which
can easily damage or cut the tubes while passing over them.
Figure 2. Installation of speed measuring devices on gravel roads
Speed Data Analysis
A total of 7,175 vehicles were observed in this study, of which 3,787 (52.8%) were measured on county
roads and 3,388 (47.2%) on township roads. Table 2 summarizes the speed data collected at the study
locations. The width of these gravel roads varied from 16 to 26 ft., and ADT ranged from 24 to 179
vehicles per day. Heavy vehicles accounted for a fairly large proportion of traffic on some gravel roads,
ranging from 4.7% to 45.8%. The 85th percentile speeds ranged from 35 to 58 mph, and mean speeds
ranged from 29 to 49 mph.
Liu, Dissanayake
4
Table 2. Summary of Speed Studies on Gravel Roads in Riley County, Kansas
Road
Type1
C
C
C
C
Road
Width
(ft)
24
26
24
24
Total
Volume
Observed
(vehs)
201
360
481
484
Heavy
Vehicle
(%)
45.8
37.8
20.9
4.7
ADT
(vehs/
day)
72
52
69
95
Mean
Speed
(mph)
36
49
44
36
Pace
(mph)
26-35
41-50
41-50
31-40
% in
Pace
55.6
48.6
45.2
54.3
85th
Speed
(mph)
46
58
52
44
% of
Vehicles >
55 mph
0
23.4
5.2
0.5
C
24
340
19
38
43
41-50
45
53
10.3
C
24
256
15.8
37
43
39-48
47.4
50
5.2
C
24
332
19
55
37
36-45
43.8
49
4.1
C
24
165
18.2
24
39
31-40
47.7
49
9.1
C
C
T
T
24
24
24
22
646
522
142
220
15.8
19.3
18.6
19.4
46
67
47
37
44
46
38
41
41-50
46-55
36-45
34-43
40.3
37.9
57.6
40.7
53
57
45
50
9.3
18.8
0
2.4
LK&W
N 52nd
T
T
20
20
138
359
11.9
35.2
20
91
37
34
31-40
31-40
53
38.2
44
44
0
0
Rocky Ford
T
22
529
10.7
179
29
21-30
51.2
35
0.5
Kitten Creek
T
22
160
7.1
34
34
31-40
50
40
0
Silver Creek
T
20
121
16.2
25
40
31-40
52
48
3.1
W 59th
T
22
635
22.5
103
35
31-40
47.4
43
1.3
N 48th
Union
Homestead
T
T
T
20
20
18
600
271
213
19.2
10.5
21.8
98
46
46
35
36
37
31-40
31-40
28-37
53.1
43.5
34.7
42
45
47
0
0
4
Road Name
W 32nd
Deep Creek
Daniels
Pillsbury
Crossing
Tabor Valley
#1
Tabor Valley
#2
Fairview
Church #1
Fairview
Church #2
Alembic
Walsburg
Marlatt
N 60th
Note: 1. C denotes county roads and T denotes township roads.
County Roads vs. Township Roads
The comparison of average speed data between county and township roads is presented in Table 3. On
average, county roads were 3.4 ft. wider than township roads and had relatively smaller ADT than
township ones. The average 85th percentile speed on county roads was 51.1 mph, which was 16.4%
higher than that on township roads (43.9 mph). The percent of vehicles traveling over 55 mph was 9.2%
on county roads, which is 0.8% higher than that on township roads (8.4%). The average mean speed and
pace on county roads were, respectively, 5.7 and 6 mph higher than on township roads. The percent in
pace on county roads was 2% less than on township roads. The percent of heavy vehicles was also 1.2%
higher on county roads than on township ones.
Liu, Dissanayake
5
Table 3. Speed data based on road types
Road type
County
Township
Combined
Road
Width
(ft)
24.2
20.8
22.4
Total
Volume
Observed
(vehs)
3,787
3,388
7,175
Heavy
Vehicle
(%)
19.9
18.7
19.3
ADT
(vehs/
day)
55.5
66
61
Mean
Speed
(mph)
41.7
36
38.7
Pace
(mph)
37-46
31-40
34-43
% in
Pace
45.5
47.4
46.4
85th
% of
Speed Vehicles >
(mph)
55 mph
51.1
9.2
43.9
8.4
47.3
5.2
Bad Weather vs. Normal Condition
Speed data were also analyzed for different weather conditions. Four types of weather conditions were
considered: snow (including snowpacked surface), rain, fog, and clear. A total of 373 vehicles were
observed under bad weather conditions, of which 201 vehicles were in snow or on a snowpacked surface,
164 were in rain, and 8 were in fog. The speed data is presented in Table 4. It is obvious that weather has
an influence on the traffic on gravel roads. All the speed values under bad weather conditions are lower
than those under clear conditions. No vehicle exceeded 55 mph under bad weather conditions. The 85th
percentile speed and mean speed in snow were slightly higher than those in rain, while the percent of
traffic in pace in snow was larger than that in rain.
Table 4. Speed data under different weather conditions
Mean Speed
Pace
85th Speed
% of Vehicles >
Weather
(mph)
(mph)
% in Pace
(mph)
55 mph
Snow
36
26-35
55.6
46
0
(snowpacked)
Rain
33
31-40
38.6
43
0
Fog*
35
N/A
N/A
N/A
0
Clear
38.7
34-43
46.4
47.3
5.2
* Only mean speed was computed due to the small number of observations under fog condition.
Moreover, speed data was compared between weekday and weekend. However, no meaningful difference
was found.
COUNTY SURVEY
A questionnaire survey was developed specially for county engineers to solicit their opinions and
comments on speed limit–related issues on gravel roads. A total of 105 counties were contacted, 59
(56.2%) counties have returned their responses to date, and more responses are hoped to be received in
the following months. Questions in the survey covered the following topics:
•
•
•
Basic information of gravel roads, including mileage, proportion by deterioration, maintenance
frequency, funding, gravel type, and source
Issues of speed limits on gravel roads, such as whether and how speed limits are posted, criteria
and manners of setting speed limits, and public complaints received
Opinions on the acceptability of blanket speed limits and speed zones
Liu, Dissanayake
6
•
Rank of the importance of thirteen factors that are likely to have an impact on setting speed
limits on gravel roads
Most of the responses included sufficient input, and 25 of them provided valuable additional comments.
Most of the questions were multiple choice and thus can be quantified. Table 5 is a summary of these
responses. Questions 1 to 5 concern specific information about gravel roads in each county and therefore
are not presented here. Questions 7 to 12 consist of information regarding how counties are implementing
speed limits and their opinions toward setting speed limits on gravel roads. Question 13 solicits
supplementary comments from those positive respondents.
Table 5. Summary of answers to county survey questions (number responding: 59, or 56.2%)
Questions
Question #6
Are there speed limits posted
on special sections of gravel
roads?
Question #7
Are there speed limits posted
on general sections of gravel
roads?
Question #8
Criteria used on setting speed
limits? (multiple choices)
Question #9
How are speed limits
adopted?
Question #10
Ever received any public
complaints on gravel roads?
What kinds of complaints
have been received?
(multiple choices)
Liu, Dissanayake
Number of
Responses
Answers
Yes
No
59
30
29
%
100
50.8
49.2
Yes
No
59
18
41
100
30.5
69.5
58
28
24
10
1
1
10
55
26
20
12
59
59
0
52
43
37
30
28
25
5
5
6
98.3
48.3
41.4
17.2
1.7
1.7
17.2
93.2
47.3
36.4
21.8
100
100
0
88.1
72.9
62.7
54.5
47.5
45.5
8.5
8.5
10.2
1. Statutory regulations/Blanket speed limit
2. Engineering study
3. Professional judgment
4. Public hearing
5. Public survey
6. Other
1. Applied to all the gravel roads
2. In special speed zones
3. Other
Yes
No
1. Poor road conditions
2. Dust Pollution
3. Vehicle speeding
4. High speeds
5. Narrow width
6. Safety
7. Low speeds
8. Noise
9. Other
7
Table 5. Continued
Question #11
Respondents’ opinions on
establishing speed limits on
gravel roads? (multiple
choices)
Question #12
Rank the importance of listed
factors when establishing
speed limits on gravel roads.
Note:
H = High;
M = Moderate;
L = Low;
N = None.
Question #13
Comments on the
acceptability of the criteria
currently used in setting
speed limits on gravel roads.
Liu, Dissanayake
1. Use BSL and do not post it on roads.
2. Prefer a lower speed limit than 55 mph for
gravel roads.
3. Prefer speed zones on some roads because they
work better than BSL.
4. Only some roads need speed limits and the rest
do not need.
5. A BSL does not contribute traffic safety.
6. Use blanket speed limit and post it on roads.
7. Prefer a higher speed limit than 55 mph for
gravel roads.
8. Other (specified by respondents):
a. Recommend 55 mph as the BSL,
b. Speeds should be regulated depending
on the amount of traffic and existing
conditions,
c. No speed limit unless needed for safety.
Factors\Importance
1. Surface condition
2. Sight distance
3. Accident history
4. Road damage by heavy
vehicles
5. Road width
6. Statutory regulations
7. Curvature
8. Traffic volume
9. 85th percentile speed
10. Roadside development
11. Maintenance period
12. Road length
13. Public attitude towards
speed regulations
58
40
22
98.3
69.0
37.9
9
15.5
6
10.4
4
3
1
6.9
5.2
1.7
6
4
10.4
6.9
H
38
35
32
29
%
69.1
63.6
58.2
52.7
M
13
16
17
17
1
55
%
23.6
29.1
30.9
30.9
26
25
23
19
16
11
11
6
5
47.3
45.5
41.8
34.5
29.1
20.0
20.0
10.9
9.1
22
19
23
22
22
29
29
15
24
40.0
34.5
41.8
40.0
40.0
52.7
52.7
27.3
43.6
Summary of comments:
1. The enforcement of speed limits on gravel roads
is a problem. Insufficient enforcement would leave
posted speed limits in a dilemma.
2. The State Statutes is preferred to control the
safety on gravel roads.
3. There is no need to post speed limit on gravel
roads.
4. Funds are critical for routine maintenance and
posting speed limit signs on gravel roads.
1.7
L
2
2
4
4
4
6
5
9
13
12
6
26
20
%
3.6
3.6
7.2
7.2
93.2
N
1
1
1
2
%
1.8
1.8
1.8
3.6
7.2
10.9
9.1
16.4
23.6
21.8
10.9
47.3
36.4
1
2
1
1
2
2
4
5
3
1.8
3.6
1.8
1.8
3.6
3.6
7.2
9.1
5.5
25
42.4
8
13.6
5
8.5
4
6.8
2
3.4
8
As summarized in Table 5, of the 59 responding counties, 50.8% have speed limit signs posted at special
sections, and 30.5% have speed limit signs posted at general sections on gravel roads. Statutory regulation
on BSL is the leading criteria for setting speed limits in 48.3% of these counties, followed by engineering
study and professional judgment.
All the responding counties have received complaints on gravel roads from the public. Poor road
condition was the one most frequently reported, 88.1% of the counties having received it, and the next
were dust pollution (72.9%), vehicle speeding (62.7%), high speeds (54.5%), narrow width (47.5), and
safety (45.5%).
Fifty-eight counties (98.3%) responded to Question 11. Sixty-nine percent of the counties supported
adoption of an unposted BSL for gravel roads, and 5.2% of the counties supported a posted BSL. Of the
respondents, 15.5% preferred speed zones to a BSL. About 10.4% thought that only some roads need
speed limits and the rest do not need them. As for speed limits on gravel roads, 37.9% of the counties
preferred a value lower than 55 mph, and 10.4% preferred the 55 mph BSL unchanged. Only 1.7%
preferred a value higher than 55 mph.
Question 12 shows the rank of importance of the factors to account for when establishing speed limits on
gravel roads. Surface condition was recognized as the most important factor by 69.1% of the respondents.
The following important factors were, in order, sight distance, accident history, surface damage by heavy
vehicles, road width, statutory regulations, curvature, and traffic volume. 85th percentile speed ranked in
the ninth position and was supported by only 29.1% of the respondents. Public attitude towards speed
regulations and road length were the two least important factors. It was noted that 74.5% of the
respondents ranked traffic volume as highly or moderately important, though traffic volume on gravel
roads is very low (usually under 100 vehicles per day) and has very limited influence on speed
distribution and crash risk.
Additionally, eight counties mentioned that if speed limits were posted on gravel roads the enforcement
would be very difficult because most counties do not have enough police officers to patrol gravel roads.
Otherwise, it is a dilemma that posted speed limits are not patrolled and are therefore overlooked by
drivers.
CRASH ANALYSIS
Analysis of crash data was performed to find out the impact of speed limits on crash severity and to
identify other critical factors that have influence on crash severity or are interrelated with speed limits on
gravel roads. The KARS database, maintained by KDOT, was used in this study. KARS consists of
details of all police-reported crash data on public roads in Kansas. To reduce the influence of the lapse of
time, a time period of 2003–2005 was considered, and relevant data was extracted from the original data
set. Contingency table testing was applied to identify the significance of relationships between two
variables from a set of thirteen variables that had been identified from KARS. Table 6 lists the categories
of these variables.
Liu, Dissanayake
9
Table 6. Categories of the variables for crashes on gravel roads
Variables
Speed limit
Crash severity
Accident class
Contributing circumstances
Collision with other vehicles
Collision with fixed object
Driver age group
Driver factor
Driver gender
Light condition
Road characteristics
Surface condition
Weather condition
Categories
30 mph, 35 mph, 40 mph, 45 mph, 50 mph, and 55 mph.
Fatal, Disabled, Non_incapacitating, Possible injured, and Not injured.
Non-collision, Overturned, Collision with other vehicle, Animal, and Fixed Object.
Driver, Environment, Road, and Vehicle.
Head on, Rear end, Angle-side impact, Sideswipe, and Backed-into.
Utility devices, Fence/gate, Ditch, Embankment, and Tree.
Old ( 65 years), Middle (>25&<65 years), and Young ( 25 years).
Too fast for conditions, Inattention, Under the influence of alcohol,
Avoidance/Evasive action, Fail to yield the right of way, and Exceeding posted
speed limit.
Female and male.
Daylight, Dawn, Dusk, and Dark.
Straight and Curve.
Dry, Wet, Snow/Slush, Ice/Snowpacked, and Mud/Dirt/Sand.
No adverse conditions, Rain, Snow, Fog/Smoke, and Strong Wind.
Source: KARS, KDOT, 2007
Speed limits were found to have significant impacts on the distribution of crashes by severity. As shown
in Table 7, roads with higher speed limits were likely to have a bigger percentage of injury crashes than
roads with lower speed limits. The biggest proportion of fatal crashes occurred on 50 mph gravel roads,
and then on 55 and 45 mph roads. Disabled crashes accounted for the biggest percentage on 45 mph
roads, and then on 40 and 55 mph. Gravel roads with a speed limit no higher than 30 mph had the
smallest percent of injury crashes. Additionally, 45 mph roads gravel roads had the largest percentage of
severe crashes (fatal and disabled), and 50 mph roads had the largest percentage of injury crashes.
Table 7. Percentage of crashes on gravel roads for different speed limits and crash severities
Speed limit
(mph)
30
35
40
45
50
55
Fatal
0.0%
0.6%
0.0%
1.2%
1.5%
1.3%
Disabled
1.4%
3.2%
3.9%
6.6%
2.3%
3.5%
Crash severity
Non-incapacitating Possible Injured
10.7%
10.3%
16.3%
9.8%
11.7%
13.6%
12.6%
8.9%
18.8%
15.0%
16.9%
11.5%
Not Injured
77.5%
70.1%
70.9%
70.7%
62.4%
66.8%
Total
100%
100%
100%
100%
100%
100%
The results of the contingency table test are presented in Table 8. Whether two variables are significantly
dependent on each other at the 95% level can be determined from the comparison of chi square computed
and chi square table. If the chi square computed is larger than the chi square table, the null hypothesis that
the two variables are independent is rejected. In Table 8, it can be seen that most of the chi square
computed values were larger than the corresponding chi square table values, except for the one between
speed limit and driver gender. Therefore, it was concluded that all the 11 variables have significant
impacts on the severity of gravel road crashes and are closely interrelated with speed limits, except for
driver gender. In other words, the gender of drivers did not show significant influence upon the crashes on
gravel roads at different speed limits.
Liu, Dissanayake
10
Table 8. Summary of crash analysis results on gravel roads
Variables
Accident class
Contributing
circumstances
Collision with other
vehicles
Collision with fixed
object
Driver age group
Driver factors
Driver gender
Light condition
Road Characteristics
Surface condition
Weather condition
Crash severity
chi
chi square square 95% Confidence chi square
Dependence
Computed
Computed Table
1549.8
21.03
1160.6
857.5
21.03
243.0
Speed limit
chi
square 95% Confidence
Table
Dependence
21.03
16.92
186.2
15.51
209.0
21.03
176.5
26.30
283.0
21.03
191.6
161.4
82.9
116.0
9.9
141.7
49.6
15.51
31.41
9.488
16.92
7.815
21.03
21.03
36.1
226.0
1.38
579.9
41.6
56.5
24.6
12.59
25.00
7.815
21.03
7.815
21.03
21.03
×
CONCLUSIONS
Field study showed that traffic speeds were distinct on gravel roads with different road characteristics and
under different weather conditions, though the speed limits on these roads were uniformly regulated by
the State Statues. The crash analysis also supported the idea that many variables have shown impacts on
both the severity of crashes and the crash frequency on gravel roads with a variety of speed limits.
Therefore, a feasible speed limit should take into account those critical factors that are likely to affect
traffic safety on gravel roads, such as the factors discussed above.
Many of the county engineers were in favor of a lowered regulatory speed limit for gravel roads, while a
few engineers strongly recommended leaving the 55 mph regulatory speed limit unchanged. Though the
popular belief is that a lower speed limit would contribute to less severe crashes, the crash analysis has
not agreed with this point. The roads with speed limits of 45 mph and 50 mph had slightly higher
percentages of fatal and disabled crashes than 55 mph roads. If the regulatory speed limit were lowered
from 55 mph to 45 or 50 mph, no evidence would ensure the decrease of severe crashes on gravel roads.
As the issues of safety and high speeds on gravel roads very much concern the public, as indicated by the
survey, another survey is being developed targeting rural residents who use gravel roads on a daily basis.
As many of the county engineers mentioned, speed limit is effective in controlling the traffic only after it
is posted on the roads and well enforced. However, it is not easy for most of the counties to achieve this,
since quite a few counties emphasized that the road funds are not sufficient for these endeavors.
Therefore, other than altering the regulatory speed limit, some other approaches could be taken to achieve
safer driving on gravel roads, such as driver education and graduated licensing, which have been proven
to very effective in other studies (Levy 1990; TRB 1996).
Liu, Dissanayake
11
REFERENCES
FHWA. 2005. Highway Statistics. Federal Highway Administration, Office of Highway Policy
Information. http://www.fhwa.dot.gov/policy/ohpi/hss/hsspubs.htm
Levy, D.T. 1990. Youth and Traffic Safety: The Effects of Driving Age, Experience, and Education.
Accident Analysis and Prevention, 22, 327–334.
Russell, E.R., R. Ewy, T.E. Mulinazzi, B.L. Smith, and E.D. Landman. 1996. Coordination of Local Road
Classification with The State Highway System Classification: Impact and Clarification of Related
Language in The LVR Manual. K-TRAN: KSU/KU-94-2. Topeka, KS: Kansas Department of
Transportation, Kansas State University and University of Kansas.
TRB. 1996. Graduate Licensing: Past Experience and Future Status. Transportation Research Circular
458. Washington, DC: Transportation Research Board, National Research Council.
USDOT. 2001. Summary of State Speed Laws Fifth Edition: Current as of January 1, 2001. U.S.
Department of Transportation, National Highway Traffic Safety Administration.
http://www.nhtsa.dot.gov/people/injury/enforce/speedlaws501/Content_SPEED.htm
USDOT. 2007. Fatality Analysis Reporting System (FARS) web-based encyclopedia. U.S. Department of
Transportation, National Center for Statistics and Analysis. http://www-fars.nhtsa.dot.gov
Liu, Dissanayake
12