ASTM E3380/E3380M-23

Standard Test Method for Evaluating Ground Response Robot Endurance Using Reproducible Terrains

SIGNIFICANCE AND USE
5.1 This test method is part of an overall suite of related test methods that provide repeatable measures of robotic system mobility and remote operator proficiency. The operational endurance of a ground robot significantly impacts the performance of the robot during a variety of tasks. Robot endurance is a complex function of robot design, control scheme design, and energy storage selection. This test method evaluates the endurance of a robot through continuous operation on a complex surface. The continuous pitch/roll ramp terrain chosen for endurance testing specifically challenges robotic system locomotion, suspension systems to maintain traction, rollover tendencies, self-righting in complex terrain (if necessary), chassis shape variability (if available), and remote situational awareness by the operator. As such, it can be used to represent modest outdoor terrain complexity or indoor debris within confined areas. The endurance test standard provides a method in which the operational endurance of a large variety of robot sizes and locomotion system designs may be compared. The test provides both a measure of the endurance of the robot and a measure of the reliability of the robot when operating continuously for extended periods of time on complex terrains.  
5.2 The scale of the terrain apparatus can vary to provide different constraints depending on the typical obstacle spacing of the intended deployment environment. For example, the terrain with containment walls can be sized to represent repeatable complexity within bus, train, or plane aisles; dwellings with hallways and doorways; relatively open parking lots with spaces between cars; or unobstructed terrains.  
5.3 The test apparatuses are low cost and easy to fabricate so they can be widely replicated. The procedure is also simple to conduct. This eases comparisons across various testing locations and dates to determine best-in-class systems and operators.  
5.4 Evaluation—This test method can be used i...
SCOPE
1.1 This test method is intended for remotely operated ground robots operating in complex, unstructured, and often hazardous environments. It specifies the apparatuses, procedures, and performance metrics necessary to measure the mission endurance of a robot while traversing complex terrains in the form of continuous pitch/roll ramps or other standard terrains in the terrain suite. This test method is one of several ground robot tests that can be used to evaluate overall system capabilities.  
1.2 The robotic system includes a remote operator in control of all functionality, so an onboard camera and remote operator display are typically required. Assistive features or autonomous behaviors that improve the effectiveness or efficiency of the overall system are encouraged.  
1.3 Different user communities can set their own thresholds of acceptable performance within this test method for various mission requirements.  
1.4 Performing Location—This test method may be performed anywhere the specified apparatuses and environmental conditions can be implemented.  
1.5 Units—The International System of Units (SI Units) and U.S. Customary Units (Imperial Units) are used throughout this document. They are not mathematical conversions. Rather, they are approximate equivalents in each system of units to enable use of readily available materials in different countries. The differences between the stated dimensions in each system of units are insignificant for the purposes of comparing test method results, so each system of units is separately considered standard within this test method.  
1.6 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.  
1.7 This international standard was develo...

General Information

• Status: Published
• Publication Date: 31-Mar-2023
• ICS: 25.040.30 - Industrial robots. Manipulators
• Technical Committee: E54 - Homeland Security Applications
• Drafting Committee: E54.09 - Response Robots

Relations

• Refers: ASTM E2826/E2826M-20 - Standard Test Method for Evaluating Response Robot Mobility Using Continuous Pitch/Roll Ramp Terrains
• Effective Date: 01-Mar-2020
• Refers: ASTM E2827/E2827M-20 - Standard Test Method for Evaluating Response Robot Mobility Using Crossing Pitch/Roll Ramp Terrains
• Effective Date: 01-Mar-2020
• Refers: ASTM E2828/E2828M-20 - Standard Test Method for Evaluating Response Robot Mobility Using Symmetric Stepfields Terrains
• Effective Date: 01-Mar-2020
• Refers: ASTM E2991/E2991M-17 - Standard Test Method for Evaluating Response Robot Mobility: Traverse Gravel Terrain
• Effective Date: 01-Sep-2017
• Refers: ASTM E2992/E2992M-17 - Standard Test Method for Evaluating Response Robot Mobility: Traverse Sand Terrain
• Effective Date: 01-Sep-2017
• Refers: ASTM E2592-16 - Standard Practice for Evaluating Response Robot Capabilities: Logistics: Packaging for Urban Search and Rescue Task Force Equipment Caches
• Effective Date: 01-Jan-2016
• Refers: ASTM E2592-07 - Standard Practice for Evaluating Cache Packaged Weight and Volume of Robots for Urban Search and Rescue
• Effective Date: 01-Oct-2007
• Refers: ASTM E2521-07a - Standard Terminology for Urban Search and Rescue Robotic Operations
• Effective Date: 01-Aug-2007
• Refers: ASTM E2521-07 - Standard Terminology for Urban Search and Rescue Robotic Operations
• Effective Date: 01-Feb-2007

Overview

ASTM E3380/E3380M-23: Standard Test Method for Evaluating Ground Response Robot Endurance Using Reproducible Terrains provides a consistent approach for measuring the operational endurance and reliability of ground response robots when operating continuously on challenging, yet repeatable, terrain. Developed by ASTM Committee E54 on Homeland Security Applications, this test method is designed for remotely operated ground robots typically deployed in complex, unstructured, or hazardous environments.

This standard supports manufacturers, researchers, emergency responders, and decision-makers by offering a means to benchmark robot performance and operator proficiency for various mission requirements. The method specifies reproducible terrain apparatuses, procedures, and performance metrics, allowing fair comparisons of different robot sizes, configurations, and operating conditions.

Key Topics

• Robot Endurance Measurement: The standard outlines procedures for assessing operational endurance by testing robots on continuous pitch/roll ramp terrains or other standardized challenging surfaces.
• Reproducible Terrain Design: Terrain apparatuses are easily fabricated and scalable, representing environments such as building hallways, transportation aisles, or open outdoor spaces, enabling repeatable and controlled testing.
• Performance Metrics: Comprehensive metrics include distance traveled (primary), runtime (secondary), and efficiency (tertiary), enabling quantitative assessment of endurance under consistent conditions.
• Operator Proficiency: As remote operators control the robots, the test also serves as a measure of operator skill and system interaction under endurance conditions.
• Comparison Across Systems: Standardized floors and procedures enable direct comparison of robot models and configurations, as well as performance tracking across locations and over time.
• Safety Considerations: Guidance is provided on emergency stop systems, safe test operation, and hazard mitigation to ensure the protection of personnel and equipment.

Applications

• Research and Development: Benchmarking new robot designs, evaluating control schemes, and assessing the impact of energy storage solutions on operational endurance in varied environments.
• Procurement and Acceptance Testing: Supporting informed purchasing decisions by aligning robot performance with end-user requirements and mission contexts.
• Operator Training and Assessment: Serving as a repeatable task for developing and verifying operator proficiency and maintaining high skill levels across deployment teams.
• System Validation for Emergency Response: Evaluating robots intended for search and rescue, hazardous material response, or disaster recovery to ensure their performance matches real-world deployment needs.
• Global Usability: The use of both SI and U.S. customary units allows the test method to be applied internationally, accommodating locally available materials and practices.

Related Standards

• ASTM E2826/E2826M: Test Method for Evaluating Response Robot Mobility Using Continuous Pitch/Roll Ramp Terrains
• ASTM E2827/E2827M: Test Method for Evaluating Response Robot Mobility Using Crossing Pitch/Roll Ramp Terrains
• ASTM E2828/E2828M: Test Method for Evaluating Response Robot Mobility Using Symmetric Stepfields Terrains
• ASTM E2991/E2991M: Test Method for Evaluating Response Robot Mobility: Traverse Gravel Terrain
• ASTM E2992/E2992M: Test Method for Evaluating Response Robot Mobility: Traverse Sand Terrain
• ASTM E3349/E3349M: Test Method for Evaluating Ground Robot Capabilities and Remote Operator Proficiency: K-Rails
• ASTM E2521: Terminology for Evaluating Response Robot Capabilities

These related standards, along with ASTM E3380/E3380M-23, form a comprehensive suite for evaluating robotic mobility, dexterity, endurance, and operator competency across different scenarios and terrain complexities.

Keywords: ground response robot, robot endurance, robotic mobility, operational testing, terrain apparatus, operator proficiency, endurance test, reproducible terrain, ASTM E3380/E3380M-23, remote robots, homeland security robotics.

Standards Content (Sample)

This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation: E3380/E3380M − 23
Standard Test Method for
Evaluating Ground Response Robot Endurance Using
Reproducible Terrains
This standard is issued under the fixed designation E3380/E3380M; the number immediately following the designation indicates the year
of original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval.
A superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
INTRODUCTION
The robotics community needs ways to measure whether a particular robot is capable of performing
specific missions in complex, unstructured, and often hazardous environments. These missions require
various combinations of elemental robot capabilities. Each capability can be represented as a test
method with an associated apparatus to provide tangible challenges for various mission requirements
and performance metrics to communicate results. These test methods can then be combined and
sequenced to evaluate essential robot capabilities and remote operator proficiencies necessary to
successfully perform intended missions.
The ASTM International Standards Committee on Homeland Security Applications (E54) specifies
these standard test methods to facilitate comparisons across different testing locations and dates for
diverse robot sizes and configurations. These standards support robot researchers, manufacturers, and
user organizations in different ways. Researchers use the standards to understand mission
requirements, encourage innovation, and demonstrate break-through capabilities. Manufacturers use
the standards to evaluate design decisions, integrate emerging technologies, and harden systems.
Emergency responders and soldiers use them to guide purchasing decisions, align deployment
expectations, and focus training with standard measures of operator proficiency. Associated usage
guides describe how these standards can be applied to support various objectives.
Several suites of standards address these elemental capabilities including maneuvering, mobility,
dexterity, sensing, endurance, communications, durability, proficiency, autonomy, and logistics.
1. Scope 1.3 Different user communities can set their own thresholds
of acceptable performance within this test method for various
1.1 This test method is intended for remotely operated
mission requirements.
ground robots operating in complex, unstructured, and often
hazardous environments. It specifies the apparatuses,
1.4 Performing Location—This test method may be per-
procedures, and performance metrics necessary to measure the
formed anywhere the specified apparatuses and environmental
mission endurance of a robot while traversing complex terrains
conditions can be implemented.
in the form of continuous pitch/roll ramps or other standard
1.5 Units—The International System of Units (SI Units) and
terrains in the terrain suite. This test method is one of several
U.S. Customary Units (Imperial Units) are used throughout this
ground robot tests that can be used to evaluate overall system
document. They are not mathematical conversions. Rather,
capabilities.
they are approximate equivalents in each system of units to
1.2 The robotic system includes a remote operator in control
enable use of readily available materials in different countries.
of all functionality, so an onboard camera and remote operator
The differences between the stated dimensions in each system
display are typically required. Assistive features or autono-
of units are insignificant for the purposes of comparing test
mous behaviors that improve the effectiveness or efficiency of
method results, so each system of units is separately considered
the overall system are encouraged.
standard within this test method.
1.6 This standard does not purport to address all of the
This test method is under the jurisdiction of ASTM Committee E54 on
safety concerns, if any, associated with its use. It is the
Homeland Security Applications and is the direct responsibility of Subcommittee
responsibility of the user of this standard to establish appro-
E54.09 on Response Robots.
priate safety, health, and environmental practices and deter-
Current edition approved April 1, 2023. Published April 2023. DOI: 10.1520/
E3380_E3380M-23. mine the applicability of regulatory limitations prior to use.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
E3380/E3380M − 23
1.7 This international standard was developed in accor- 120 cm 6 2.5 cm tolerance [48 in. 6 1 in. tolerance], such
dance with internationally recognized principles on standard- as indoor spaces in accessibility-compliant buildings;
ization established in the Decision on Principles for the 60 cm 6 1.3 cm tolerance [24 in. 6 0.5 in. tolerance],
Development of International Standards, Guides and Recom- residences and aisles of public transportation; or
mendations issued by the World Trade Organization Technical 30 cm 6 1.3 cm tolerance [12 in. 6 0.5 in. tolerance],
Barriers to Trade (TBT) Committee. cluttered indoor spaces, ductwork, and voids in collapsed
structures.
2. Referenced Documents
3.3.1.1 Discussion—The measures for these scales are
nominal and do not represent the measurement of the narrowest
2.1 ASTM Standards:
point in the apparatus through which the robot should pass.
E2521 Terminology for Evaluating Response Robot Capa-
Consult Section 6 for the overall measurements and dimen-
bilities
sions of the apparatus at each scale.
E2592 Practice for Evaluating Response Robot Capabilities:
Logistics: Packaging for Urban Search and Rescue Task
3.3.2 quarter-ramp terrain element, n—inclined surface of
Force Equipment Caches
15° with square dimensions as projected onto the ground plane
E2826/E2826M Test Method for Evaluating Response Ro-
equal to ⁄4 the overall width of the test lane.
bot Mobility Using Continuous Pitch/Roll Ramp Terrains
4. Summary of Test Method
E2827/E2827M Test Method for Evaluating Response Ro-
4.1 This test method is performed by a remote operator, out
bot Mobility Using Crossing Pitch/Roll Ramp Terrains
of sight and sound of the robot, while controlling the robot
E2828/E2828M Test Method for Evaluating Response Ro-
within the test apparatus. The robot follows one of two defined
bot Mobility Using Symmetric Stepfields Terrains
paths in the specified terrain requiring the robot to overcome
E2991/E2991M Test Method for Evaluating Response Ro-
challenges including pitch, roll, traction, and turning on uneven
bot Mobility: Traverse Gravel Terrain
surfaces within open or confined spaces.
E2992/E2992M Test Method for Evaluating Response Ro-
bot Mobility: Traverse Sand Terrain
4.2 The figure-8 path (forward) is a continuous forward path
E3349/E3349M Test Method for Evaluating Ground Robot
through the terrain with alternating left and right turns to avoid
Capabilities and Remote Operator Proficiency: Terrains:
barriers. It can be used to demonstrate terrain traversal over
K-Rails
long distances within a relatively small apparatus. The con-
2.2 Other Document: tinuous traverse is shown as the white path (see Figs. 1 and 2).
NIST Special Publication 1011-I-3.0 Autonomy levels for
4.3 The zig-zag path (forward/reverse) is an end-to-end path
unmanned systems (ALFUS) Framework Volume I: Ter-
that requires forward and reverse traversal through the terrain
minology
with alternating left and right turns to avoid barriers. This can
be used to demonstrate traversal of the terrain within confined
3. Terminology
spaces. The down-range traverse, shown as the white path, is
3.1 Definitions—The following terms are used in this test
performed in a forward orientation and the up-range traverse,
method and are defined in Terminology E2521: abstain,
shown as the black path, is performed in reverse (see Fig. 1 and
administrator or test administrator, emergency response robot
Fig. 3).
or response robot, fault condition, operator, operator station,
4.4 The robot starts on one side or the other of a lane full of
remote control, repetition, robot, teleoperation, test event or
fabricated continuous ramp terrain at a chosen scale. The robot
event, test form, test sponsor, test suite, testing target or target,
follows either the figure-8 path (forward) or the zig-zag path
testing task or task, and trial or test trial.
(forward/reverse) between the two barriers.
3.2 The following terms are used in this test method and are
4.5 The figure-8 path (forward) repetition is completed
defined in ALFUS Framework Volume I:3: autonomous,
when the robot crosses the start/end centerline of the lane
autonomy, level of autonomy, operator control unit (OCU), and
without a fault after approximately following the white path.
semi-autonomous.
The zig-zag path (forward/reverse) repetition is completed
3.3 Definitions of Terms Specific to This Standard:
when the robot returns to the starting point after crossing the
3.3.1 apparatus clearance width (W), n—a specification for
plane at the end of the barrier without a fault after approxi-
the apparatus dimensions chosen from one of four possible
mately following the white and black paths.
measurements, based on the intended robot deployment envi-
4.6 The terrain may be extended to create a larger turning
ronment:
area for the figure-8 path and more room to fit past the plane at
240 cm 6 2.5 cm tolerance [96 in. 6 1 in. tolerance], such
the end of the barrier in the zig-zag path (see Fig. 2 and Fig. 3).
as open and outdoor public spaces;
The distance per repetition remains the distance between the
outer edges of the barriers (see Section 6) regardless of the
actual distance traveled.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
4.7 Potential Faults Include:
Standards volume information, refer to the standard’s Document Summary page on
4.7.1 Any contact by the robot with the apparatus (that is,
the ASTM website.
walls or barriers) that requires adjustment or repair to return the
Available from National Institute of Standards and Technology (NIST), 100
Bureau Dr., Stop 1070, Gaithersburg, MD 20899-1070, http://www.nist.gov. apparatus to the initial condition;
E3380/E3380M − 23
FIG. 1 Overview of the Continuous Pitch/roll Ramp Terrain Apparatus
FIG. 2 Top View showing the Figure-8 Path (forward) defined by the Barriers
4.7.2 Any visual, audible, or physical interaction that assists operators often have erratic ten-lap segment times which could
either the robot or the remote operator; and
affect the validity of the performance metrics.
4.7.3 Leaving the apparatus during the trial.
4.9 There are three metrics to consider when calculating the
4.8 The endurance test is unique in that a complete test
results of a test trial. They should be considered in the
running until exhaustion of the energy source on the robot is
following order of importance: distance traveled, runtime, and
required to calculate the performance metrics of distance
efficiency. The results from the figure-8 path (forward) and the
traveled and runtime. During the test, the higher the ratio of
zig-zag path (forward/reverse) are not comparable because
successful repetitions to faults, the more reliable the system or
they measure different capabilities. The results from different
operator, or both. At least 90 % of the attempted repetitions in
scales of test apparatus are also not comparable because they
an endurance test should be successful to consider the perfor-
represent different clearances and distances.
mance metrics as valid measurements of endurance. The time
required to complete each series of ten laps is an indicator of
5. Significance and Use
operator performance. If the operator is consistently driving the
robot around the track, the time for each ten-lap segment 5.1 This test method is part of an overall suite of related test
methods that provide repeatable measures of robotic system
should be very similar. This is also an indication that the energy
required for each ten lap segment is similar. Inexperienced mobility and remote operator proficiency. The operational
E3380/E3380M − 23
FIG. 3 Top View showing the Zig-Zag Path (forward/reverse) defined by the Barriers
endurance of a ground robot significantly impacts the perfor- training scenarios to measure degradation due to uncontrolled
mance of the robot during a variety of tasks. Robot endurance variables in lighting, weather, radio communications, GPS
is a complex function of robot design, control scheme design, accuracy, etc.
and energy storage selection. This test method evaluates the
5.5 Procurement—This test method can be used to identify
endurance of a robot through continuous operation on a
inherent capability trade-offs in systems, make informed pur-
complex surface. The continuous pitch/roll ramp terrain chosen
chasing decisions, and verify performance during acceptance
for endurance testing specifically challenges robotic system
testing. This aligns requirement specifications and user expec-
locomotion, suspension systems to maintain traction, rollover
tations with existing capability limits.
tendencies, self-righting in complex terrain (if necessary),
5.6 Training—This test method can be used to focus opera-
chassis shape variability (if available), and remote situational
tor training as a repeatable practice task or as an embedded task
awareness by the operator. As such, it can be used to represent
within training scenarios. The resulting measures of remote
modest outdoor terrain complexity or indoor debris within
operator proficiency enable tracking of perishable skills over
confined areas. The endurance test standard provides a method
time, along with comparisons of performance across squads,
in which the operational endurance of a large variety of robot
regions, or national averages.
sizes and locomotion system designs may be compared. The
test provides both a measure of the endurance of the robot and
5.7 Innovation—This test method can be used to inspire
a measure of the reliability of the robot when operating technical innovation, demonstrate break-through capabilities,
continuously for extended periods of time on complex terrains.
and measure the reliability of systems performing specific tasks
within an overall mission sequence. Combining or sequencing
5.2 The scale of the terrain apparatus can vary to provide
multiple test methods can guide manufacturers toward imple-
different constraints depending on the typical obstacle spacing
menting the combinations of capabilities necessary to perform
of the intended deployment environment. For example, the
essential mission tasks.
terrain with containment walls can be sized to represent
repeatable complexity within bus, train, or plane aisles; dwell-
6. Apparatus
ings with hallways and doorways; relatively open parking lots
with spaces between cars; or unobstructed terrains. 6.1 The apparatus required to perform this test method
consists of an operational terrain type, barriers to define the
5.3 The test apparatuses are low cost and easy to fabricate
robot path, an optional containment structure, and a timer. The
so they can be widely replicated. The procedure is also simple
main apparatus dimension to consider is the apparatus clear-
to conduct. This eases comparisons across various testing
ance width (W) for the robot, which can be set to 240 cm 6
locations and dates to determine best-in-class systems and
2.5 cm tolerance [96 in. 6 1 in. tolerance], 120 cm 6 2.5 cm
operators.
tolerance [8 in. 6 1 in. tolerance], 60 cm 6 1.3 cm tolerance
5.4 Evaluation—This test method can be used in a con- [24 in. 6 0.5 in. tolerance], or 30 cm 6 1.3 cm tolerance
trolled environment to measure baseline capabilities. The [12 in. 6 0.5 in. tolerance]. The dimension chosen for W
endurance test apparatus can also be embedded into operational should represent the intended deployment environment or be
E3380/E3380M − 23
based on the size of the robot (that is, the robot shall be able to 6.2.1.1 Crossing Pitch/Roll Ramps—Test Method E2827/
maneuver within the selected dimensions of the apparatus), or E2827M;
both. All apparatus dimensions scale proportionally with W;
6.2.1.2 Symmetric Stepfields—Test Method E2828/
the overall width of the terrain lane is 2W, the overall length of
E2828M;
the terrain lane is at least 6W, the length of the barriers is 1W,
6.2.1.3 Gravel Terrain—Test Method E2991/E2991M;
and the distance is 2W between the barriers. It can be longer for
6.2.1.4 Sand Terrain—Test Method E2992/E2992M; and
larger robots needing more space to maneuver around the
6.2.1.5 K-Rails—Test Method E3349/E3349M.
barriers while staying on the terrain. When choosing a specific
minimum clearance width for the apparatus, note the resulting
6.3 Barriers to Define the Robot Path—The barriers placed
data is not comparable to other apparatuses with different
within the terrain must provide visual guidance for the remote
minimum clearance widths.
robot operator to correctly traverse the defined figure-8 path
(forward) or zig-zag path (forward/reverse). The barrier can be
6.2 Pitch/Roll Ramp Terrain—The primary terrain type for
endurance testing is the 15° continuous pitch/roll ramp terrain. made from any solid or porous material that provides visual
The continuous pitch/roll ramp terrain is an array of individual guidance. They should be sturdy and easily repaired or
ramps that form peaks and valleys with no discontinuities replaced in case of contact with the robot. The barrier’s overall
greater than 0.05W. Each ramp is fabricated to fit a square thickness shall be less than 0.05W and the length shall equal
1W.
dimension on the ground so it can be rotated in place to form
more difficult terrains. The square ground dimension is set to
6.4 Containment Structure—While a containment structure
half the minimum clearance width ( ⁄2 W) so apparatuses at
is not necessary, it may be used as an additional safety
every scale have a maximum gap (no greater than 0.05W)
measure. The fabricated wood walls are typically supported
between ramps along the centerline of the lane to accommodate
with arches over the top. Shipping containers can also enclose
the width of the barriers (see Fig. 6). The ramp surface can be
test methods and turn a parking lot into a test facility.
made of oriented strand board (OSB), plywood, or similar
Apparatuses with clearance width W = 120 cm [4 ft] can be
material to provide a relatively consistent low-friction surface.
slightly undersized to fit into a standard shipping container,
The supporting structure can be fabricated from lumber posts
which has an interior width that is less than 240 cm [8 ft]. The
and OSB panels. Each ramp is fabricated to fit a square
container walls should be lined with wood panels to cover the
dimension on the ground for interchangeability, so the 15°
corrugated steel and have enough thickness to fill any gaps
ramp surface is slightly longer than ⁄2 W in the uphill
between the wall and the terrain, if necessary. The array of
dimension. The width remains ⁄2 W. Four lumber posts cut
individual pitch/roll ramps need to be contained so they do not
with 15° tops provide support for the ramp surface and connect
move relative to one another (see Fig. 8). The minimum
the three side panels that provide additional support and
containment is an underlayment with an affixed lumber
...