USER GUIDE for USLIMITS2

December 2017
1 

Contents

Contents ..................................................................................................................................................... 1

Background................................................................................................................................................. 2

Objective of this Guide ............................................................................................................................... 2

Accessing the Expert System....................................................................................................................... 3

Getting Started ........................................................................................................................................... 3

Revise/Update Existing Projects ................................................................................................................. 3

Creating New Projects................................................................................................................................. 4

New Route .................................................................................................................................................. 4

Existing Route: Selecting a Route and Area Type........................................................................................ 4

Input Variables.......................................................................................................................................... 18

Project Review.......................................................................................................................................... 33

Output ...................................................................................................................................................... 33

Examples................................................................................................................................................... 36

Decision Rules ..........................................................................................................................................K-1
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Background 

Speed limits are selected to balance travel efficiency versus safety. It can be argued that a 

rational speed limit is one that is safe, that most people consider appropriate, that will protect the 

public, and can be enforced. Many practitioners also feel that better methods are needed to

identify appropriate speed limits especially in urban roads having higher traffic volumes, a mix of

road users, and more roadside activity. Many practitioners and researchers have argued that a

knowledge-based expert system can provide assistance to the practitioner in setting the

appropriate speed limit for specific conditions on a road section.

Expert systems for recommending maximum posted speed limits have been used in Australia for 

more than a decade starting in the late 1980’s. The first expert system (VLIMITS) was developed

for the province of Victoria by the Australian Road Research Board (ARRB). 

Subsequently systems were developed for different provinces in Australia and New Zealand.

These systems are collectively referred to as the XLIMITS programs. Based on their experience

in developing the XLIMITS programs, FHWA contracted with ARRB to adapt XLIMITS for use

in the USA, but with changes made to reflect speed setting philosophy in this country (such as

posting in 5 mi/h multiples). This resulted in the USLIMITS Version 1.0. 

Version 2 of the expert system described in this user guide (hereafter called USLIMITS2)

employs a decision algorithm to advise the user of the appropriate maximum speed limit for the

specific road section of interest. Unlike the original version, USLIMITS2 was developed based

on input from a panel of experts in the USA that included traffic engineers, enforcement

personnel, decision makers, and researchers from different parts of the country. The expert

system is accessed through the Internet and provides recommended speed limits for speed zones

on all types of roadways from rural two-lane roads to urban freeway segments. The types of

speed limits not addressed by the system include statutory limits such as maximum limits set by

State legislatures for Interstates and other roadways, temporary or part-time speed limits such as

limits posted in work zones and school zones, and variable speed limits that are raised or lowered

based on traffic, weather, and other conditions. 

Objective of this Guide

The primary objective of this guide is to assist the user in recommending an appropriate

maximum speed limit for specific conditions on a road section. The guide provides information

needed to use the USLIMITS2 system. Included is a section on “Getting Started” which is

followed by detailed definitions of the variables that are used in the expert system, descriptions of 

the data that need to be collected by the user, and the results that can be expected from this

program. Example applications for a variety of road and area conditions are included to illustrate

the input and output results for typical speed zoning situations. 

For details regarding the decision rules that were used to develop this expert system, users should 

refer to the Decision Rules document that can also be downloaded from the expert system.
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Considerable effort has been expended to check the appropriateness of the maximum speed limit

recommendations made by USLIMITS2, however, the user is responsible for collecting and 

inputting the information requested by the program. Engineering experience and knowledge 

should be used in collecting the required information and when interpreting the results.

Accessing the Expert System

Since this program is accessed through the Internet the user is only required to have a computer 

with web-browsing software connected to the Internet. Any web browser version developed in 

2003 or later would be sufficient. Examples include Netscape (Version 6.0 or later), MS Explorer 

(Version 5.5 or later), and Firefox (Version 0.8 or later). 

USLIMITS2 uses session cookies, meaning cookies are not stored permanently on your computer

and are deleted once your browser is closed. Please note that you must have cookies enabled in 

your browser for the program to work correctly. To do so, go to the security settings in your 

browser and ensure that it is set to allow cookies. 

The final results are output to the user’s computer screen and can be saved in a Microsoft Word 

file, a Microsoft Excel file, a PDF, and a project file (.txt file). Users do not need any special 

skills to access and use the system. However, to obtain useful results from the system, the user is 

required to provide specific engineering and crash information about the road section that is being 

examined.

Getting Started

The original version of the USLIMITS2 program asked users to create an account. With the 

transfer of USLIMITS2 to the FHWA server, there are no user accounts anymore. 

The user is asked to either create a new project or revise/update an existing project. In order to be 

able to revise/update an existing project, the user should have a .txt file in their local computer that

was created while using this application for a project.

A “HELP” tab is provided on the Home Page as well as successive screens to provide the user with

background information on the expert system. This information includes a brief description of the 

site background, the complete NCHRP 3-67 Final Report, this User Guide for USLIMITS2, and 

flow charts illustrating the decision rules used in the system.

Revise/Update Existing Projects

If the user has already created projects in USLIMITS2 and saved the information as .txt files on 

their computer, they can upload them into the system and revise/update them.

When the user clicks on ‘Revise or Update an Existing Project’, they will be taken to a window

that will allow them to browse their computer for projects that they had created earlier.

Once the user has identified the project that they want to edit, they can ‘submit’ it by clicking on 

the ‘submit’ button. 

The user will then be able to update all variables for the project and resubmit the project. A

description of each of these variables is given in the “Input Variables” section of this guide. 
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Creating New Projects

Selecting “Create a New Project” will take the user to the “NEW PROJECT ENTRY” screen. The 

user is required to input or select from a pull-down menu, the following information: 

• State

• County 

• City/Area

• Your Name 

• Route/Street Name

• Study Segment Start and End (This input is optional) 

• New or Existing Route 

• Existing Speed Limit (This input is optional. The existing speed limit is not factored into 

the recommended speed limit but is meant to help the user document all information about 

the study area.) 

• Route Type, i.e., Limited Access Freeway, Road Section in Undeveloped Area, and Road

Section in Developed Area. (See guidance below for assistance in selecting a route type.) 

• Project Date, i.e., the current date or any date the user selects.

• Project/File Name (At the completion of the USLIMITS2 process, an output file will be

created that contains all of the entered data. The Project/File Name input, with the entry

date appended, will be used as the default name for the output file.)

• Project Number (This input is optional) 

• Project Description (This input is optional and is used to record any information the user

wishes such as purpose of study, requesting source, study dates, etc.) 

After the project description information is entered, the user is required to press the “Submit”

button to go to the next screen and input the engineering data for the road segment under 

investigation. This input is described in the “Input Variables” section of this guide. 

New Route

If the user indicates that this project is for a new route, the system will only ask for the Statutory 

Speed Limit. As new roads will not have any crash or speed data, USLIMITS2 recommends that 

the statutory speed be posted on new routes until such time that reliable data on operating speed, 

crashes, and other factors can be collected.

Existing Route: Selecting a Route and Area Type

Selecting a Route and Area Type is an extremely important step in using the expert system.

Guidance is provided in this section to assist the user in selecting the appropriate Route and Area

Type for the road or street segment they are studying.

This expert system has three primary sets of decision rules corresponding to the following three

route types: Limited Access Freeway, Road Sections in Undeveloped Areas, and Road Sections in

Developed Areas.

GUIDANCE: The identification of freeways and expressways sections with limited access control 

is straightforward because these road segments do not have at-grade intersections or other direct

access features such as driveways, signals, on-street parking, etc. However, distinguishing

between a road section in an undeveloped area and a road section in a developed area can
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sometimes be challenging because the study road segment may have both rural and urban 

characteristics. For example, a road in an undeveloped area may have one traffic signal and 

several residential and small business driveways. Conversely, a road segment in a developed area

may not have any residential or commercial driveways, or traffic signals. When the user is in

doubt as to which category a study section falls, it is suggested that two analyses be performed. 

The first analysis should be conducted using a road section in an undeveloped area, and the second 

analysis should be conducted assuming a road segment in a developed area. The results of these

analyses should be compared to identify which analysis best describes the study section

characteristics.

Definitions of each route and area type along with photographs illustrating typical characteristics

of these sections are given in the following paragraphs. 

Limited Access Freeway – This route type includes U.S. and state numbered freeways and 

expressways and Interstate routes where access to and from the facility is limited to interchanges

with grade separations. Opposing directions of travel are separated by a median on these highspeed routes which typically have posted speed limits ranging from 55 mph in urban areas to 75 

mph in some rural states. Some urban areas may have short segments directly connecting the

freeway to surface streets where the posted speed limit is as low as 35 mph. Photographs of typical

freeway sections are shown later in this document.

Users should select this category only when they desire to obtain a speed limit recommendation for 

a limited access facility with grade separated intersections. If the facility includes at-grade 

intersections, then the user should select either Road Sections in Undeveloped Areas or Road 

Sections in Developed Areas depending on the area type defined later in this section.

NOTE: During the development of this expert system, the project team decided that the system

should provide maximum speed limit recommendations for street and road segments based on 

existing knowledge and experience. At that time, the highest maximum speed limit on limited

access highways in the United States was 75 miles per hour. Consequently, the maximum speed

limit recommended by USLIMITS2 is 75 miles per hour. 

The reason for imposing a 75 mile per hour upper limit was to prevent users in the United States

from receiving a recommended speed limit that was not based on empirical evidence and the 

knowledge and experience of experts. For example, a recommended speed limit of 85 miles per 

hour on a freeway would not be recommended in this system because currently there is very little

evidence to suggest how and under what conditions such a limit would be appropriate. 

As of December 2017, the highest legal permitted maximum speed limit in the United States is 85

miles per hour for passenger cars on State Highway 130 in Texas. Sections of I-10 and I-20 in 

West Texas and sections of Highway 45 in Travis County have a speed limit for passenger cars 

and light trucks of 80 mph. Speed limits of up to 85 mph may be established if the highway is 

originally constructed and designed to accommodate the higher speed and it has been determined 

by an engineering study to be reasonable and safe. In Utah, the speed limit may be increased 

beyond 75 mph on any freeway or limited access highway on the basis of an engineering and 

traffic investigation. The highest posted limit in Utah is currently 80mph. In Wyoming, the speed 

limit may be increased to 80 mph on specific segments of highway on the basis of an engineering 

and traffic investigation. In Idaho, the speed limit may be increased to 80 mph on specific 
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segments of highway on the basis of an engineering and traffic investigation. In Oklahoma, the 

speed limit may be increased by the DOT beyond 75 mph on any highway or part of a highway 

based on an engineering and traffic investigation, effective November 1, 2016. (Source: 

http://www.iihs.org/iihs/topics/laws/speedlimits/mapmaxspeedonruralinterstates?topicName=Speed) 

In the future, when additional experience with 80 mile per hour and higher speed limits has 

occurred in the United States and the empirical evidence suggests that these limits are acceptable, 

then an increase in the recommended maximum limit could be considered in the next revision of 

USLIMITS2. 

Road Section in Undeveloped Area – An undeveloped area is generally an area where the human 

population is low and the roadside primarily consists of the natural environment with some built 

elements such as utility poles, fences, and an occasional driveway. Access to the road is not 

restricted and posted speed limits are typically in the 40 mph to 65 mph range depending upon 

terrain and road design features. Rural road sections with lower speed limits usually have 

narrower pavement widths, little or no shoulders, and horizontal and vertical curvature that limits 

driver speeds. Rural road sections with higher speed limits usually have improved geometric 

design features such as 12-foot lanes, 8-foot or greater shoulders which may be paved, and 

horizontal and vertical curvature that supports higher travel speeds. Photographs of typical road 

sections in undeveloped areas are shown below. 

Users should select this category only when they desire to obtain a speed limit recommendation

for a rural road section. Roads in undeveloped areas usually do not have the features found in

urban or developed areas such as on-street parking, traffic signal systems, sidewalks, curb and 

gutter, street lighting, frequent driveways and public street intersections serving homes and 

businesses, etc. Also pedestrian and bicycle activity is generally minor in undeveloped areas.

NOTE: As previously noted, during the development of this expert system, the project team

decided that the system should provide maximum speed limit recommendations for street and 

road segments based on existing knowledge and experience. While there were a few exceptions,

at the time of initial development of USLIMITS2, the highest maximum speed limit in rural areas 

in the United States was 65 mph. Consequently, the maximum speed limit recommended by 

USLIMITS2 was set at 65 mph. 

In the future, when additional experience with 70 mph and higher speed limits on two- lane and 

other rural roads has occurred in the United States and the empirical evidence suggests that

these limits are acceptable, then an increase in the recommended maximum limit could be

considered in the next revision of USLIMITS2. 

Road Section in Developed Area – A developed or built-up area is an area where the built 

environment has generally replaced most of the natural environment. Access is not restricted and

posted speed limits are usually in the 25 mph to 50 mph range depending on geometric design of 

the facility. Urban road sections with lower speed limits are found in downtown and residential

areas with considerable pedestrian and other non-motorized movements, on-street parking 

activity, numerous driveways serving residential and commercial development, and traffic signal

systems. Urban road sections with higher speed limits have been designed to have little

pedestrian activity, no on-street parking, and traffic control which favors through traffic 

movement. Routes in this category include one-way streets.
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NOTE: As previously noted, during the development of this expert system, the project team

decided that the system should provide maximum speed limit recommendations for street and 

road segments based on existing knowledge and experience. While there may be some

exceptions, at that time the maximum speed limit on urban surface streets in the United States

was approximately 50 mph. Consequently, the maximum speed limit recommended by

USLIMITS2 was set at 50 mph. Roads and streets within city boundaries may have posted speed

limits higher than 50 mph; however, these streets typically have geometric design and traffic

characteristics more similar to rural roads and limited access freeways.

In the future, when additional experience with 55 mph and higher speed limits on urban roads in

built up areas has occurred in the United States and the empirical evidence suggests that these

limits are acceptable, then an increase in the recommended maximum limit could be considered 

in the next revision of USLIMITS2. 

Roads in developed areas are further subdivided into residential subdivision/neighborhood 

street, residential collector street, commercial street, and a street serving a large complex such as

a major shopping mall, university or medical complex, etc. Definitions as well as photographs 

illustrating the features of typical road sections in developed areas are shown on the following 

pages.

Residential Subdivision/Neighborhood Street – A residential neighborhood street is a public 

street located within a subdivision or group of homes that serves the motorized and nonmotorized activities of residents. Posted speed limits generally range from 25 to 35 mph. Twoway traffic operations are permitted along with on-street parking on both sides of the road, 

however, the pavement width is typically too narrow to allow unimpeded bidirectional traffic and 

on-street parking. These streets usually do not carry through traffic. Commercial development is

not permitted in the area.

Residential Collector or Arterial Street – An arterial street through a predominately residential 

area primarily caters to through traffic. A residential collector street carries both through traffic 

from residential neighborhoods and local traffic generated by residents who live along the 

corridor. Posted speed limits generally range from 25 mph to 45 mph. The pavement widths 

permit full time operation of bidirectional traffic. On-street parking on one or both sides may or 

may not be permitted. Development along the street is primarily single- and multi-family homes. 

Typically there are more than 30 residential driveways per mile. The corridor may contain a 

small amount of commercial development; usually convenience stores at major intersections.

Commercial Street – A commercial street is a street that serves both through traffic and local

commercial activities. Development along the corridor is primarily commercial with more than 30 

business driveways per mile. Posted speed limits generally range from 25 mph to 45 mph. The 

streets usually tend to be multilane and on-street parking on one or both sides may or may not be 

permitted.
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Street Serving Large Complexes – Large area business developments typically include shopping 

malls, office buildings and industrial complexes. Streets that serve large complexes generally are 

designed to carry large volumes of traffic to and from the complex and typically are designed to

manage access to carry through volumes. The streets tend to be multilane facilities and the number 

of access driveways is usually less than 30 per mile. Posted speed limits generally range from 35 

mph to 50 mph.

Photographs illustrating the different road and area types are shown as follows. 

Limited Access Freeway – Includes Interstate, US and other routes where access is limited to 

grade separated crossings. The systems are located in rural and urban areas.
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10

Road Section in Undeveloped Area - Includes roads in rural areas. The road section may have

some scattered development with typically less than 30 commercial and residential driveways

per mile. Posted speed limits are usually in the 40 to 65 mph range. 
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Road Section in Developed Area – Includes roads in built-up areas. Posted speed limits

typically range from 25 to 50 mph depending upon road and development conditions. Specific

categories of roads in developed areas include; 

1. Residential Subdivision/Neighborhood Street

2. Residential Collector Street

3. Commercial Street

4. Street Serving Large Complexes 

Residential Subdivision/Neighborhood Street – Predominately includes streets serving a group 

of homes or subdivisions that provides motorized and non-motorized trips for local residents. 

Posted speed limits usually range from 25 to 35 mph. 
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14

Residential Collector or Arterial Street – Includes mostly residential single-family homes and 

multi-family development with more than 30 driveways per mile.
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Commercial Street – Includes mostly shopping and service business with typically more than

30 driveways per mile. This category also includes downtown streets.
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Street Serving Large Complexes – Includes shopping malls, office buildings, industrial

complexes, etc. There are high volume driveways. The number of driveways is usually less than

30 per mile
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For each route type, the following input variables are required: Limited

Access Freeway

Operating Speed: 85th percentile speed and 50th percentile speed Section

Length

Annual Average Daily Traffic 

Presence/absence of adverse alignment 

Current statutory speed limit for this type of road 

Terrain

Is this section transitioning to a non-limited access highway?

Number of Interchanges within this section

Crash Statistics

Road Section in Undeveloped Area

Operating Speed: 85th percentile speed and 50th percentile speed Section

Length

Annual Average Daily Traffic Presence/absence of adverse alignment 

Current statutory speed limit for this type of road 

Is this section transitioning to a road section in a developed area?

Roadside Rating 

Divided/Undivided Section Number of through lanes (in both directions) 

Crash Statistics

Road Sections in Developed Areas

Operating Speed: 85th percentile speed and 50th percentile speed Section

Length

Annual Average Daily Traffic Presence/absence of adverse alignment

Current statutory speed limit for this type of road 

 Whether it is a One-Way Street?

Number of Through Lanes (in both directions) 

Area Type

Number of driveways within the section

Number of traffic signals within the section

Presence/usage of on-street parking 

Extent of ped/bike activity

Crash Statistics

The following paragraphs provide a detailed description of each of these input variables. 
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Input Variables

Operating Speed

85th Percentile Speed – The 85th percentile speed is the speed at or below which 85 percent of

the drivers travel on a road segment. The 85th percentile speed should be taken from speed data

collected during a 24-hour weekday period. Typically the data are collected with commercially

available roadside units which sort and present the results in text as well as graphical format. 

Speed studies should be conducted using the format and procedures described in your

jurisdiction’s publications for establishing speed zones. If your jurisdiction does not have a

specific written procedure, additional information is found in the ITE Manual of Transportation

Engineering Studies, November 2010. 

The road cross section of the speed zone segment being studied should be uniform with similar

roadside development. If the number of lanes, road function, or development changes with a 

study section, the segment should be further subdivided with the measurement of 85th percentile

speeds in each segment. Another factor that should be taken into consideration when

determining the start and end points of a speed zone is the location of adverse-alignment such as

sharp horizontal curves, where the advisory speed may be less than the speed limit. The 85th

percentile speed used in the analysis for a general speed limit should not be taken from data

collected in the adversely aligned section.

This program is not designed to handle the unusual situations where the 85th percentile speed on 

limited access freeways is less than 35 mph, less than 25 mph on road sections in undeveloped 

areas, or less than 20 mph on road sections in developed areas. If a portion of the section has 

adverse alignment or the section is a transition zone, the program will allow users to enter 85th

percentile speeds less than 45 mph (but higher than 35 mph) on freeways, and less than 35 mph 

(but higher than 25 mph) on road sections in undeveloped areas.

50th Percentile Speed – The 50th percentile speed is the speed at or below which 50 percent of

the drivers travel on a road segment. The 50th percentile speed should be taken from speed data

collected during a 24-hour weekday period. In this program, the difference between the 85th

percentile speed and the 50th percentile speed cannot exceed 15 mph. 

Adverse Alignment

Adverse alignment of the road includes road features with vertical and/or horizontal alignments

which differ significantly from the alignment of the general road. Adverse alignment segments

typically have poor sight distance, reverse curves, and other features such as narrow pavement

widths and shoulders that reduce operating speeds below the general speed limit for the section.

When adverse alignment is present in a study section, a warning will be provided along with the 

general recommended speed limit for the section. Sections with adverse 
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alignment typically require posting advisory speed warnings which are lower than the general

speed limit for the section. This program does not suggest numerical values that can be used to

determine the advisory speed warnings for adverse alignment. If adverse alignment is present,

the system gives the following warning as part of the recommended speed limit:

Sections with adverse alignments may need specific advisory speed warnings which may be 

different from the general speed limit for the section. See Procedures for Setting Advisory

Speeds on Curves for more guidance, Publication No. FHWA-SA-11-22, June 2011. 

Transition Zone

For projects on limited access freeways, users are asked to indicate if this section is transitioning

to a non-limited access road. For projects with road sections in undeveloped areas, users are 

asked if the section is transitioning to a road section in a developed area. The answers are mainly

used to determine if the operating speed is too low for a particular roadway type – lower

operating speeds are typically used in transition zones. 

Section Length

This refers to the length of the study section in miles.

Statutory Speed Limit

This refers to the statutory speed limit for this type of road in that jurisdiction. Statutory speed

limits are limits established by legislative authority and are generally applicable throughout a 

political jurisdiction. Users should consult the vehicle codes in their state or jurisdiction to

determine the statutory limit for the type of facility under study. Many of the laws are available

on-line at the state or the local jurisdiction web site. If the recommended speed limit is higher

than the statutory limit, the system provides a warning message. Users have the option of 

selecting “None” for states that do not have a statutory speed limit.

Terrain (only for Limited Access Freeways)

Terrain is classified as Level/Flat, Rolling, or Mountainous which is defined in the following 

paragraphs. 

Level/flat:

Level/flat terrain is that condition where highway sight distances, as governed by both horizontal 

and vertical restrictions, are generally long. Maximum freeway grades are typically less than 3 

percent in flat terrain.

Rolling:

Rolling terrain is that condition where the natural slopes consistently rise above and fall below 

the road grade and where occasional steep slopes offer some restriction to normal horizontal and 

vertical roadway alignment. Maximum freeway grades are typically less than 4 percent in rolling 

terrain.
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Mountainous:

Mountainous terrain is that condition where longitudinal and transverse changes in the

elevation of the ground with respect to the road are abrupt. Maximum freeway grades are

typically less than 6 percent in mountainous terrain, but may exceed 7 percent in some areas.

In this program, the maximum speed limit for mountainous sections on limited access freeways 

is 70 mph. 

Annual Average Daily Traffic (AADT)

The daily flow of motor traffic is averaged out over the year to give the Average Annual Daily

AADT, a useful and simple measurement of how many vehicles use the facility during an

average day.

Number of Interchanges (only for Limited Access Freeways)

The number of interchanges within the section is used to calculate the average interchange 

spacing which is equal to the length of the section divided by the number of interchanges. If

the number of interchanges in a section is equal to zero, then the interchange spacing is set

equal to the length of the section.

Crash Statistics and Analysis

In order for the system to conduct an analysis of the crash data, the following inputs are

requested: 

• Length of the study period in years and months (FHWA recommends at least 3 years

of crash data; if less than 1 year of data are input, the program suggests that

additional data should be collected and the process repeated)

• Total number of crashes in the section

• Total number of injury and fatal crashes in the section

• The average AADT for the study period (the field is automatically populated with 

the AADT previously entered, but the user can change it if needed) 

This information is used to calculate the rate of total crashes and rate of injury and fatal

crashes per 100 million vehicle miles. The user is then asked to input the average rate of total

crashes and average rate of injury and fatal crashes (again per 100 million vehicles miles) for

similar road sections in their jurisdiction. To determine the average crash/injury rate for

similar sections, users should select a group of sections that have the same or similar

geometry, i.e., number of lanes, median type, etc., and similar traffic volumes and area type.

If the user does not provide average rates, default values from the Highway Safety Information 

System (HSIS) are used. HSIS is a multi-state database that contains crash, roadway

inventory, and traffic volume data for 8 States in the nation. In most of these states, the

information in this database is limited to state-maintained facilities. Crash rates and injury 

rates were calculated using the latest 3 years of data that were available: California (2009-11), 
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Minnesota (2010-12), North Carolina (2011-13), Ohio (2010-12), and Washington (2010-12). 

This data will be updated as soon as the latest HSIS data is available. Table 1 shows the

average crash and injury rates calculated based on HSIS data.

Table 1. Average crash and injury rates based on HSIS data (updated 2015)

ROADWAY CLASS AADT Category

Crash Rate per

100MVM

Injury & Fatal

Crash Rate per

100MVM

Urban Freeways (interchange spacing

< 1mi)

 0 - 24,999 92.83 24.74

25,000 - 49,999 79.80 21.24

50,000 - 74,999

75,000 - 99,999

100,000 - 149,999

76.96

88.34

91.16

21.37

25.15

27.69

150,000 - 199,999 91.60 29.25

200,000+ 104.51 30.75

Rural Freeways (interchange spacing > 

1mi)

0 - 24,999

25,000 - 49,999

50,000+

49.20

51.23

44.16

13.39

12.92

14.41

Urban 2 lane roads (Developed

areas)

 0 - 2,499 263.17 67.32

2,500 - 4,999 209.14 64.31

 5,000 - 7,499

 7,500 - 9,999

10,000 - 14,999

205.37

229.55

246.62

63.75

70.26

73.14

15,000 - 19,999 253.25 78.14

20,000+ 225.17 71.82

Urban multilane divided nonfreeways (Developed areas)

0 - 9,999 226.43 72.02

10,000 - 19,999

20,000 - 29,999

30,000 - 39,999

40,000 - 49,999

202.46

228.69

228.37

205.73

66.16

75.37

74.01

70.84

50,000+ 158.17 56.32

Urban multilane undivided nonfreeways (Developed areas)

0 - 9,999

10,000 - 19,999

20,000 - 29,999

30,000+

452.14

452.26

431.09

431.25

131.02

131.98

129.00

131.10

Urban one-way streets (Developed

areas)

0 - 4,999 245.12 60.21

5,000 - 9,999 139.27 37.29

10,000 - 14,999

15,000 - 19,999

20,000 - 24,999

72.18

58.31

57.36

22.79

18.19

17.72

25,000 - 29,999 63.87 20.07

30,000 + 54.63 15.03

Rural 2 lane roads (Undeveloped

areas)

 0 - 1,249 206.56 65.21

1,250 - 2,499 166.00 54.01

2,500 - 3,749 147.23 47.73

3,750 - 4,999

5,000 - 6,249

6,250 - 7,499

133.96

128.57

121.91

43.89

43.29

41.46

7,500 - 8,749 125.70 44.14
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ROADWAY CLASS AADT Category

Crash Rate per

100MVM

Injury & Fatal

Crash Rate per

100MVM

8,750 - 9,999 123.35 43.46

10,000+ 98.16 35.60

Rural multilane divided non-freeways

(Undeveloped areas)

 0 - 4,999 102.55 28.93

5,000 - 9,999

10,000 - 14,999

15,000 - 19,999

20,000 - 24,999

76.77

73.90

70.83

70.59

22.14

20.77

20.79

23.11

 25,000+ 65.56 21.28

Rural multilane undivided 0 - 4,999 153.35 50.00

non-freeways 5,000 - 9,999 145.63 42.08

(Undeveloped areas) 10,000+ 124.54 41.14

Using the average rate provided by the user or from HSIS, the system calculates a critical rate

using the following formula (see Zegeer and Deen (1977), “Identification of Hazardous

Locations on City Streets”, Traffic Quarterly, Vol. 31(4), pp. 549-570.) 

 

Where: 

RC = critical rate for a given road type

Ra = average rate for a given road type

K = constant associated with the confidence level (1.645 for 95% confidence) 

M = 100 million vehicle miles

It is important that the user/practitioner undertake a comprehensive crash study to determine 

probable causes and appropriate countermeasures that could be implemented to reduce the 

frequency and severity of crashes. If the crash and/or injury rate is higher than the corresponding 

critical value (crash or injury level is considered High in this case) or at least 30% higher than the 

corresponding average rate (crash or injury level is considered Medium in this case), the system

will ask the user if the crash or injury rate can be reduced by implementing traffic and/or 

geometric measures. Depending on the answer to this question, the system provides a 

recommended speed limit.

Roadside Rating (only for Road Sections in Undeveloped Areas)

The roadside hazard rating is a measure of roadside conditions including: shoulder width and 

type, side-slope, clear zone distance, and presence/absence of fixed objects on the roadside. 
23

The scale ranges from 1 to 7, with 1 representing the lowest hazard (best conditions), and 7

representing the highest hazard (worst conditions). These scales are based on the following work

that was conducted in the late 1980’s for the Federal Highway Administration: Zegeer, C.V.,

Hummer, J., Reinfurt, D., Herf, L., and Hunter, W., Safety Effects of Cross-Section Design for

Two-Lane Roads, Volume I-Final Report, FHWA-RD-87/008, October 1987. 

Following is a description of ratings 1 through 7. Photographs illustrating these ratings are 

provided following the description.

Rating = 1

• Wide clear zones free from obstacles greater than or equal to 9 m (30 ft) from the

pavement edgeline.

• Sideslope flatter than 1:4. 

• Recoverable in a run-off-road situation.

Rating = 2

• Clear zone free from obstacles between 6 and 7.5 m (20 and 25 ft) from pavement

edgeline.

• Sideslope about 1:4. 

• Recoverable in a run-off-road situation.

Rating = 3

• Clear zone free from obstacles about 3 m (10 ft) from pavement edgeline.

• Sideslope about 1:3 or 1:4.

• Rough roadside surface. 

• Marginally recoverable in a run-off-road situation. 

Rating = 4

• Clear zone free from obstacles between 1.5 and 3 m (5 to 10 ft) from pavement edgeline.

• Sideslope about 1:3 or 1:4.

• May have guardrail (1.5 to 2 m [5 to 6.5 ft] from pavement edgeline).

• May have exposed trees, poles, or other objects (about 3 m or 10 ft from pavement

edgeline).

• Marginally forgiving in a run-off-road situation, but increased chance of a reportable

roadside collision.

Rating = 5

• Clear zone free from obstacles between 1.5 and 3 m (5 to 10 ft) from pavement edgeline.

• Sideslope about 1:3. 

• May have guardrail (0 to 1.5 m [0 to 5 ft] from pavement edgeline).
24

• May have rigid obstacles or embankment within 2 to 3 m (6.5 to 10 ft) of pavement

edgeline.

• Virtually non-recoverable in a run-off-road situation. 

Rating = 6

• Clear zone free from obstacles less than or equal to 1.5 m (5 ft). 

• Sideslope about 1:2. 

• No guardrail. 

• Exposed rigid obstacles within 0 to 2 m (0 to 6.5 ft) of the pavement edgeline.

• Non-recoverable in a run-off-road situation.

Rating = 7

• Clear zone free from obstacles less than or equal to 1.5 m (5 ft). 

• Sideslope 1:2 or steeper.

• Cliff or vertical rock cut.

• No guardrail. 

• Non-recoverable in a run-off-road situation with a high likelihood of severe injuries from

roadside collision.
25
26
27
28
29
30
31
32

Number of Through Lanes

The user is requested to input the total number of through traffic lanes in both directions of 

travel. On a one-way street, this is the number of through lanes in one direction. 

Divided/Undivided Section

The user is asked to determine the presence/absence of a median by selecting from the

following categories:

 Undivided 

Divided

Two-Way Left-Turn-Lane (TWLTL)

One-Way Street (only for Road Section in Developed Area)

The user is asked to state if the study section is a one-way street.

Number of Driveways in the Section

This refers to the number of driveways and unsignalized access points in the section. Access

points on both sides of the road should be included in this count. This information is used to

calculate the number of driveways per mile in the section (number of driveways divided by

section length). 

Number of Traffic Signals within the Section

This refers to the number of signalized intersections in the section. Traffic signals are defined 

as stop and go signals. Flashing beacons and warning beacons should not be included in this

count. This information is used to calculate the number of signals per mile (number of signals

divided by section length). 

Presence/Usage of On-Street Parking 

Users are asked to select between ‘High’ and ‘Not High’. ‘High’ parking activity and usage

typically occur in downtown and/or CBD areas. These areas usually have parking on both

sides of the road with parking time limits that do not exceed 60 minutes, with at least 30 

percent of parking spaces occupied during weekdays.

Extent of Ped/Bike Activity

Users are asked to select between ‘High’ and ‘Not High’. Examples of areas with ‘High’

pedestrian and bicycle activity include:
33

(1) Residential developments with four or more housing units per acre interspersed

with multifamilydwellings,

(2) Hotels located with 1/2 mile of other attractions such as retail stores, recreation areas,

or senior centers,

(3) Downtown or CBD areas, and 

(4) the presence of paved sidewalks, marked crosswalks, and pedestrian signals.

Project Review

The user is given the opportunity to review all data that they have entered into the system 

before submitting the data for the final results. If the user decides to change any of their entries 

they may do so from this screen by clicking on the “Edit” button next to the relevant section 

that they want to edit.

Note: If the user wants to edit fields in any of the prior screens, they will then need to click 

Submit again on each of the proceeding screens until they get back to the Project Review page

and click “Submit” for the final time. 

Output

The expert system provides an advisory recommended maximum speed limit along with the 

necessary limitations and warnings. The output can be printed and saved in a Microsoft Word 

file, a PDF file, and a Microsoft Excel file. The Microsoft Word and Excel and PDF

files also show the data that were input by the user for a particular project. The Word file can

be formatted depending on the needs of the user. In addition, it is also possible to create a 

project file (encrypted .txt file) that can be used later for revising/updating the project. The 

.txt file is stored in the user’s computer. 

It is well known that driver response to speed limits is at least partially dependent on the

level of enforcement and the enforcement tolerance. With regard to enforcing the speed limit,

there is a wide range of unofficial enforcement tolerances used throughout the US ranging 

from 5 to 20 mph. However, a speed limit set with the assistance of this expert system

should be enforced within 5 to 7 mph of the recommended speed limit. This allows only for 

reasonable speed odometer and instrument errors. Above this limit, the motorist is exceeding

the safe and reasonable speed of traffic. 

The U.S. Government assumes no liability for the use of the information contained in the 

output report. This report does not constitute a standard, specification, or regulation. 

In addition to the recommended speed limit, the following limitations and warnings are

provided: 
34

Warnings for All Roadway Types

If the final recommended speed limit is higher than the statutory limit, the following warning 

is provided to the user:

The final recommended speed limit is higher than the statutory speed limit for this

type of road. 

If the user indicates that there is adverse alignment in the section: 

Sections with adverse alignments may need specific ‘maximum safe speed warnings’

which may be different from the general speed limit for the section. This program 

does not provide maximum safe advisory speed warnings for adverse alignments.

If Length of Section is shorter than the Minimum Section Length, then the following message

is provided: 

A section length of <Length> miles is too short for speed zoning on public streets

and roads for the recommended speed limit. You may consider lengthening the 

speed zone (if that is possible) or using the speed limits from adjacent sections (if

they are appropriate for this section). If the 85th percentile speeds and other data

you provided. are representative of conditions for this short section, then the speed

limit noted above should be considered. If the data were taken in a road section with

adverse horizontal and vertical alignment, in a construction zone, or in an area with

unique geometric and/or traffic control features, then the above noted speed limit

may not be appropriate because this expert system is not designed to recommend 

advisory speeds for sharp horizontal curves, within the limits of construction zones, 

or in other special traffic situations. 

The minimum section length for a particular speed limit is based on Table L.2 (this is

the same guideline that is used in USLIMITS 1.0 and Australian XLIMITS expert 

systems)

Table 2. Minimum Section Lengths

Speed Limit Minimum Length

30mph 0.30 miles

35mph 0.35 miles

40mph 0.40 miles

45mph 0.45 miles

50mph 0.50 miles

55mph 0.55 miles

60mph 1.20 miles

65mph 3.00 miles

70mph 6.20 miles

75mph 6.20 miles
35

If the user does not enter crash data, the following warning is provided: 

Crash data were not entered for this project. A comprehensive crash study is a critical

component of any traffic engineering study. We suggest that you repeat this process

when crash data become available.

If Crash or Injury Level is High or Medium, the following message is provided: 

The crash rate of the section is <crash_rate> per 100 MVMT. The average rate for

similar sections is <Ca> per 100 MVMT, and the critical rate is <Cc> per 100

MVMT. The crash rate of this section is <crash_diff> % higher (or lower) than the

average crash rate for similar sections. The rate of injury crashes for the section is

<injury_rate> per 100 MVMT. The average rate for similar sections is <Ia> per 100

MVMT, and the critical rate is <Ic> per 100 MVMT. The rate of injury crashes for

this section is

<Injury_diff>% higher (or lower) than the average rate for similar sections. A

comprehensive crash study should be undertaken to identify engineering and traffic

control deficiencies and appropriate corrective actions. The speed limit should only 

be reduced as a last measure after all other treatments have either been tried or ruled 

out. 

Warnings for Limited Access Freeways

If 85th percentile speed is > 77 mph, then the following warning is given: 

Based on the information gathered from experts in the U.S., this program does not

recommend speed limits higher than 75 mph. 

Warnings for Road Sections in Undeveloped Areas

If 85th percentile speed is > 67 mph, then the following warning is given: 

Based on the information gathered from experts in the U.S., this program does not

recommend speed limits higher than 65 mph for non-limited access road sections in

undeveloped areas.

Warnings for Road Sections in Developed Areas

If 85th percentile speed is > 52 mph, then the following warning is given: 

Based on the information gathered from experts in the U.S., this program does not

recommend speed limits higher than 50 mph for non-limited access road sections in

developed areas.
36

Examples

Example 1 – Speed Limit Request on a Two-Lane Road in an Undeveloped Area

The first example is a two-lane road in a rural area. At the request of the Township officials, the

engineer has been asked to conduct a traffic and engineering investigation to determine if the

existing maximum 50 mile per hour speed limit should be lowered. Based on data collected

during the investigation, the USLIMITS2 screens below show the input variables and final

suggested speed limit for this road section.

This is the Basic Location Information input screen.
37

This is the basic input screen for the 85th percentile speed and other variables.
38

This is the input screen for the crash data.
39

This is the crash summary generated by USLIMITS2 based on the crash data input by the user. 
40

This screen provides a summary of the crash calculations.
41

This is the Project Review Screen that allows the user to review and edit all submitted data. 
42

This is the final output screen showing the advisory recommended speed limit for this rural road

section.
43

The results can also be printed to a Microsoft Word or PDF file as shown below. 

USLIMITS2 Speed Zoning Report

Project Name: Example 1 - Plank Road Speed Limit Request

 

Analyst: John Doe

 

Basic Project Information

Route Name: Plank Road

State: Michigan

County: Washtenaw County

City: Rural

Route Type: Road Section in Undeveloped Area

Route Status: Existing

 

Roadway Information

Section Length: 2.12 mile(s)

Statutory Speed Limit: 55 mph

Existing Speed Limit: 50 mph

Adverse Alignment: No

Divided/Undivided: Undivided 

Number of Lanes: 2

Roadside Hazard Rating: 3

Transition Zone: No

Date: 12-11-2017

 

Crash Data Information

Crash Data Years: 3.50

Crash AADT: 1180 veh/day

Total Number of Crashes: 7

Total Number of Injury Crashes: 2

Section Crash Rate: 219 per 100 MVM

Section Injury Crash Rate: 63 per 100 MVM

Crash Rate Average for Similar Roads: 207

Injury Rate Average for Similar Roads: 65

 

Traffic Information

85th Percentile Speed: 52 mph

50th Percentile Speed: 46 mph

AADT: 1200 veh/day

Project Description: Speed limit study conducted at the request of the township.

Recommended Speed Limit: 50 

Disclaimer: The U.S. Government assumes no liability for the use of the information contained in 

this report. This report does not constitute a standard, specification, or regulation. 

Equations Used in Crash Data Calculations 

Exposure (M) 

M = (Section AADT * 365 * Section Length * Duration of Crash Data) / (100000000) 

M = (1180 * 365 * 2.12 * 3.50) / (100000000) 

M = 0.0320 

Crash Rate (Rc) 

Rc = (Section Crash Average * 100000000) / (Section AADT * 365 * Section Length) 

Rc = (2.00 * 100000000) / (1180 * 365 * 2.12) 

Rc = 219.04 crashes per 100 MVM 

Injury Rate (Ri) 

Ri = (Section Injury Crash Average * 100000000) / (Section AADT * 365 * Section Length) 

Ri = (0.57 * 100000000) / (1180 * 365 * 2.12) 
44

Ri = 62.58 injuries per 100 MVM 

Critical Crash Rate (Cc) 

Cc = Crash Average of Similar Sections + 1.645 * (Crash Average of Similar Sections / Exposure) ^ 

(1/2) + (1 / (2 * Exposure)) 

Cc = 206.56 + 1.645 * (206.56 / 0.0320) ^ (1/2) + (1 / (2 * 0.0320)) 

Cc = 354.46 crashes per 100 MVM 

Critical Injury Rate (Ic) 

Ic = Injury Crash Average of Similar Sections + 1.645 * (Injury Crash Average of Similar Sections / 

Exposure) ^ (1/2) + (1 / (2 * Exposure)) 

Ic = 65.21 + 1.645 * (65.21 / 0.0320) ^ (1/2) + (1 / (2 * 0.0320)) 

Ic = 155.17 injuries per 100 MVM 
45

Example 2 – Speed Limit Request on a Multilane Road in a Developed Area

The second example is multilane residential collector street. Based on citizen’s requests, the City

Engineer has been asked to conduct a traffic and engineering investigation to determine if the 

existing 35 mile per hour speed limit is appropriate. Utilizing the data collected during the

investigation, the USLIMITS2 screens below show the input variables and final suggested speed

limit for this road section. 

This is the Basic Location Information input screen.
46

This is the basic input screen for the 85th percentile speed and other variables.
47

This is the input screen for the crash data.
48

This is the crash summary generated by USLIMITS2 based on the crash data input by the user. 
49

This screen provides a summary of the crash calculations.
50

This is the Project Review Screen that allows the user to review and edit all submitted data. 
51

This is the final output screen showing the advisory recommended speed limit for this urban

multilane street.
52

The results can also be printed to a Microsoft Word file as shown below. 

USLIMITS2 Speed Zoning Report

Project Name: Example 2 - Oak Street Speed Limit Request

 

Analyst: Jane Doe

 

Basic Project Information

Project Number: TAY08

Route Name: Oak Street

State: Michigan

County: Wayne County

City: Taylor city

Route Type: Road Section in Developed Area

Route Status: Existing

 

Roadway Information

Section Length: 4.06 mile(s)

Statutory Speed Limit: 50 mph

Existing Speed Limit: 35 mph

Adverse Alignment: No

One-Way Street: No

Divided/Undivided: Undivided 

Number of Through Lanes: 4

Area Type: Residential-Collector/Arterial

Number of Driveways: 156

Number of Signals: 5

Date: 12-18-2017

 

Crash Data Information

Crash Data Years: 3.00

Crash AADT: 13500 veh/day

Total Number of Crashes: 76

Total Number of Injury Crashes: 18

Section Crash Rate: 127 per 100 MVM

Section Injury Crash Rate: 30 per 100 MVM

Crash Rate Average for Similar Roads: 452

Injury Rate Average for Similar Roads: 132

 

Traffic Information

85th Percentile Speed: 42 mph

50th Percentile Speed: 36 mph

AADT: 13500 veh/day

On Street Parking and Usage: Not High

Pedestrian / Bicyclist Activity: Not High

Project Description: Speed limit recheck as a result of a request by citizens.

Recommended Speed Limit: 40 

Disclaimer: The U.S. Government assumes no liability for the use of the information contained in this 

report. This report does not constitute a standard, specification, or regulation. 

Equations Used in Crash Data Calculations 

Exposure (M) 

M = (Section AADT * 365 * Section Length * Duration of Crash Data) / (100000000) 

M = (13500 * 365 * 4.06 * 3.00) / (100000000) 

M = 0.6002 

Crash Rate (Rc) 

Rc = (Section Crash Average * 100000000) / (Section AADT * 365 * Section Length) 

Rc = (25.33 * 100000000) / (13500 * 365 * 4.06) 

Rc = 126.63 crashes per 100 MVM 
53

Injury Rate (Ri) 

Ri = (Section Injury Crash Average * 100000000) / (Section AADT * 365 * Section Length) 

Ri = (6.00 * 100000000) / (13500 * 365 * 4.06) 

Ri = 29.99 injuries per 100 MVM 

Critical Crash Rate (Cc) 

Cc = Crash Average of Similar Sections + 1.645 * (Crash Average of Similar Sections / Exposure) ^ 

(1/2) + (1 / (2 * Exposure)) 

Cc = 452.26 + 1.645 * (452.26 / 0.6002) ^ (1/2) + (1 / (2 * 0.6002)) 

Cc = 498.25 crashes per 100 MVM 

Critical Injury Rate (Ic) 

Ic = Injury Crash Average of Similar Sections + 1.645 * (Injury Crash Average of Similar Sections / 

Exposure) ^ (1/2) + (1 / (2 * Exposure)) 

Ic = 131.98 + 1.645 * (131.98 / 0.6002) ^ (1/2) + (1 / (2 * 0.6002)) 

Ic = 157.21 injuries per 100 MVM 
51

Example 3 – Speed Limit Recheck on an Urban Freeway Connector

This final example is a short freeway connector that runs between a high-volume, high-speed

Interstate route and a non-limited access multilane urban arterial corridor. As a routine recheck

of posted speed limits conducted every five years, the traffic engineer has been asked to

conduct a traffic and engineering investigation to determine if the existing maximum 55 mile

per hour speed limit is appropriate for conditions. Based on data collected during the 

investigation, the USLIMITS2 screens below show the input variables and final suggested

speed limit for this freeway connector. 

This is the Basic Location Information input screen.
52

This is the basic input screen for the 85th percentile speed and other variables.
53

This is the input screen for the crash data.
54

This is the crash summary generated by USLIMITS2 based on the crash data input by the user. 
55

This screen provides a summary of the crash calculations.
56

This is the Project Review Screen that allows the user to review and edit all submitted data. 
57

This is the final output screen showing the advisory recommended speed limit and the

appropriate notes for this freeway connector. 
58

The results can also be printed to a Microsoft Word file as shown below. 

USLIMITS2 Speed Zoning Report

Project Name: Example 3 - I-75 Connector Speed Limit Recheck

 

Analyst: Jane Doe

 

Basic Project Information

Project Number: I-75 TAY 22

Route Name: I-75 Connector

State: Michigan

County: Wayne County

City: Taylor city

Route Type: Limited Access Freeway

Route Status: Existing

 

Roadway Information

Section Length: 1.76 mile(s)

Statutory Speed Limit: 70 mph

Existing Speed Limit: 55 mph

Adverse Alignment: No

Terrain: Flat

Interchanges: 1

Transition Zone: No

Date: 12-18-2017

 

Crash Data Information

Crash Data Years: 4.00

Crash AADT: 35300 veh/day

Total Number of Crashes: 21

Total Number of Injury Crashes: 5

Section Crash Rate: 23 per 100 MVM

Section Injury Crash Rate: 6 per 100 MVM

Crash Rate Average for Similar Roads: 51

Injury Rate Average for Similar Roads: 13

 

Traffic Information

85th Percentile Speed: 67 mph

50th Percentile Speed: 60 mph

AADT: 26800 veh/day

Project Description: Routine Speed Limit Recheck

Recommended Speed Limit: 65 

Note: A speed zone of 1.76 miles is generally too short for the recommended speed limit. Consider 

lengthening the speed zone (if that is possible) or using the speed limits from adjacent sections (if 

they are appropriate for this section). If the speed and other data you provided are representative of 

conditions for this short section, then the speed limit noted above may be considered. 

Disclaimer: The U.S. Government assumes no liability for the use of the information contained in this 

report. This report does not constitute a standard, specification, or regulation. 

Equations Used in Crash Data Calculations 

Exposure (M) 

M = (Section AADT * 365 * Section Length * Duration of Crash Data) / (100000000) 

M = (35300 * 365 * 1.76 * 4.00) / (100000000) 

M = 0.9071 

Crash Rate (Rc) 

Rc = (Section Crash Average * 100000000) / (Section AADT * 365 * Section Length) 

Rc = (5.25 * 100000000) / (35300 * 365 * 1.76) 
59

Rc = 23.15 crashes per 100 MVM 

Injury Rate (Ri) 

Ri = (Section Injury Crash Average * 100000000) / (Section AADT * 365 * Section Length) 

Ri = (1.25 * 100000000) / (35300 * 365 * 1.76) 

Ri = 5.51 injuries per 100 MVM 

Critical Crash Rate (Cc) 

Cc = Crash Average of Similar Sections + 1.645 * (Crash Average of Similar Sections / Exposure) ^ 

(1/2) + (1 / (2 * Exposure)) 

Cc = 51.23 + 1.645 * (51.23 / 0.9071) ^ (1/2) + (1 / (2 * 0.9071)) 

Cc = 64.14 crashes per 100 MVM 

Critical Injury Rate (Ic) 

Ic = Injury Crash Average of Similar Sections + 1.645 * (Injury Crash Average of Similar Sections / 

Exposure) ^ (1/2) + (1 / (2 * Exposure)) 

Ic = 12.92 + 1.645 * (12.92 / 0.9071) ^ (1/2) + (1 / (2 * 0.9071)) 

Ic = 19.69 injuries per 100 MVM 
K-1

APPENDIX K

FLOW CHARTS ILLUSTRATING DECISION RULES
K-2
K-3
K-4
K-5
K-6
K-7
K-8
K-9
K-10
K-11
K-12
K-13
K-14
K-15
K-16
K-17
K-18
K-19
K-20
K-21
K-22
K-23 
K-24
K-25
K-26
K-27
K-28
K-29
K-30