Comprehensive Analysis Report on Highway Guardrail Application Scenarios

1. Abstract

This report aims to comprehensively review and deeply analyze various application scenarios of highway guardrails within road safety protection systems. As crucial traffic safety facilities, guardrails serve functions far beyond simple physical isolation. They significantly reduce the severity of traffic accidents and minimize casualties by absorbing collision energy, effectively guiding vehicles, directing driver’s sight, and restricting pedestrian crossing. The report will elaborate on the principles and considerations for guardrail installation in typical highway environments such as roadsides, central medians, and bridge and tunnel entrances/exits, extending to special applications of pedestrian and non-motorized vehicle lane guardrails on urban roads.

The design and selection of guardrails are not based on a single consideration but are dynamically adjusted according to various factors such as road geometric characteristics, traffic volume, vehicle composition, and potential accident risks. For instance, in sharp curves, steep slopes, or high embankment sections, the protection level of guardrails needs to be appropriately elevated. Furthermore, the continuous development of guardrail technology, such as the application of rotating anti-collision barrel guardrails and combined guardrails, reflects the ongoing exploration in engineering to enhance safety performance, optimize cost-effectiveness, and ensure environmental compatibility. These developments indicate a trend towards smarter and more sustainable infrastructure construction.

2. Introduction

2.1 Role and Significance of Guardrails in Road Safety Protection Systems

Highway guardrails are an indispensable safety component of modern transportation infrastructure, with their core function being to actively or passively ensure the safety of road users. From a passive protection perspective, the primary task of guardrails is to prevent out-of-control vehicles from deviating from their intended path, avoiding them from running off the roadside, entering opposing lanes, or falling from high-risk areas such as bridges or elevated structures, thereby effectively curbing severe traffic accidents. This protective mechanism absorbs the immense energy generated during vehicle collisions and ensures that vehicles are effectively blocked or redirected after impact, thereby minimizing occupant injuries and property damage.

However, the role of guardrails extends beyond this. They also serve an active safety guidance function, for example, by their continuous structure guiding the driver’s sight, especially at night or in adverse weather conditions with low visibility, providing drivers with clear road boundaries and directional guidance. Concurrently, as physical isolation facilities, guardrails effectively deter pedestrians from crossing motorized vehicle lanes indiscriminately, maintaining traffic order and ensuring pedestrian safety. This dual role—passive protection and active guidance—embodies the core principle of “people-oriented, safety first” in road safety design. This principle prioritizes human life and minimizes harm, transcending mere structural integrity or traffic efficiency considerations, and becoming a deeply embedded social value in infrastructure construction. Guardrail design not only focuses on vehicle dynamic response during accidents but also delves into considerations of human behavior and perception, thus forming a more comprehensive and refined road safety protection system.

2.2 Report Objectives, Scope, and Structure

This report aims to comprehensively review the application scenarios of highway guardrails in various complex environments, deeply analyzing their functional characteristics, design principles, and selection considerations. The scope of the report will cover guardrail applications on highways, urban roads, and in temporary traffic management, and will explore their impact on the safety of vehicles, pedestrians, and non-motorized vehicles. The report structure will systematically elaborate on guardrail functions, classifications, typical application scenarios, design considerations, and future developments, striving to provide an authoritative and practical reference for professionals in relevant fields.

3. Basic Functions and Classification of Guardrails

3.1 Core Safety Functions of Guardrails

Guardrails play multiple critical roles in road traffic safety, with their core functions including:

Preventing vehicle deviation, penetration, straddling, or under-running: This is the most basic and important function of guardrails. When a vehicle deviates from its normal driving path due to various reasons (e.g., loss of control, fatigued driving, speeding), guardrails can effectively block it, preventing the vehicle from running off the roadside, entering opposing lanes, or falling from high places like bridges or elevated structures, thereby avoiding more severe accidents.
Absorbing collision energy to minimize accident losses: Guardrails are designed to absorb the vehicle’s collision energy through their own structural deformation or, in some cases, by forcing the vehicle to climb. This energy absorption mechanism significantly reduces the impact force on the vehicle and its occupants, thereby minimizing casualties and property damage. Guardrail design focuses not only on preventing vehicles from leaving the road but, more importantly, on managing the consequences after a vehicle leaves the road, including minimizing occupant injuries and preventing secondary accidents. This indicates that guardrail design involves a complex understanding of vehicle dynamics and human biomechanics to achieve safer outcomes in collision scenarios.
Guiding vehicle direction and maintaining normal driving state: Guardrails should possess good guidance capabilities, meaning that after a vehicle collides, they should smoothly guide it back to its normal driving direction, preventing the vehicle from overturning, turning around, or other dangerous situations that could lead to secondary accidents. The buffering and guiding performance of guardrails are important indicators of their safety effectiveness.
Guiding driver’s sight and deterring pedestrian crossing: The continuous structure of guardrails is crucial for guiding the driver’s sight, especially at night or in adverse weather conditions, as it enhances road visibility and helps drivers maintain the correct driving direction. Simultaneously, as a physical barrier, guardrails effectively deter pedestrians from crossing the road indiscriminately, thereby maintaining traffic order and ensuring pedestrian safety. This consideration of environmental factors (such as headlight glare) and human behavior (driver’s sight, pedestrian crossing) expands the functional scope of guardrails, making them a multi-dimensional risk management component within the road safety system, beyond mere physical collision protection.

3.2 Structural Types and Characteristics of Guardrails

Guardrails come in various structural types, and their selection typically depends on the road environment, design requirements, and anticipated protection level. Based on the degree of deformation after collision, guardrails can be classified into rigid, semi-rigid, and flexible types.

Rigid Guardrails:

Main Representative: Concrete guardrails.
Characteristics: Structurally robust, not easily deformed upon impact, primarily absorb collision energy by forcing the vehicle to climb. Due to their rigid nature, they prevent vehicle penetration, but the impact on the vehicle and occupants during a collision can be significant.
Typical Applicable Scenarios: Suitable for sections where minimal deformation is required or high-energy collisions need to be withstood, such as central medians of highways, outer sides of bridges, and sections with a high proportion of large vehicles.
Semi-Rigid Guardrails:

Main Representative: W-beam guardrails and box beam guardrails.
Characteristics: Undergo a certain degree of deformation upon impact, absorbing energy through this deformation, while also possessing good guidance, allowing colliding vehicles to smoothly return to their normal driving direction. W-beam guardrails are the most common type.
Typical Applicable Scenarios: Widely used on roadsides, central medians, and various other scenarios, especially on sections requiring a balance between protective performance and a certain deformation space.
Flexible Guardrails:

Main Representative: Cable guardrails.
Characteristics: Supported by tensioned cables (steel ropes), possessing significant deformation capacity, effectively absorbing collision energy. Their advantage lies in effective buffering and reducing vehicle damage. However, due to their large deformation, they are not suitable for sections with small curve radii.
Typical Applicable Scenarios: Suitable for sections requiring large buffer space and where deformation requirements are relatively lenient.

Supplementary Notes on Common Structural Forms:

W-beam Guardrails: The most common type of protective barrier, consisting of corrugated cross-section beams and cylindrical supports, with advantages of simple and convenient installation and relatively low cost.
Box Beam Guardrails: Use large box-shaped steel as beams, suitable for narrow separators.
Combined Guardrails: Combine the advantages of different materials or structural forms, such as combined W-beam steel guardrails. These guardrails aim to balance multiple design objectives, such as achieving high anti-collision capability (e.g., SBm level) while occupying less driving width, providing good sightlines, being easy to install, and having relatively low cost. However, it should be noted that even advanced combined guardrails have specific limits to their protective capabilities. For example, for 49-ton heavy semi-trailers with enormous initial kinetic energy, W-beam guardrails may not be able to fully absorb the energy through their own deformation and prevent them from penetrating the central median.⁵ This indicates that as the proportion of heavy vehicles in traffic composition increases, existing guardrail technology still faces challenges, requiring continuous technological innovation to cope with extreme collision conditions.

Auxiliary Facilities:

In addition to the main structure, guardrail systems often integrate various auxiliary facilities to further enhance road safety:

Anti-glare Facilities: Installed on median guardrails, such as anti-glare nets, anti-glare panels, metal nets, or trees planted in the median (e.g., privet, azaleas), aiming to prevent glare from oncoming vehicle headlights from affecting drivers, ensuring safe and smooth night traffic. For example, on the inner side of bridges, except for sections with anti-litter nets, other sections can be installed with green synthetic resin or fiberglass anti-glare panels, having specific anti-glare angles.
Buffer Facilities: Such as buffer drums (typically yellow plastic containers filled with water), anti-collision barrels, or crash cushions, installed before fixed structures like road divergence edges, roadside piers, or road signs, used to reduce the impact of vehicle collisions and prevent occupant injuries.
Warning Facilities: Flashing lights installed at road divergence ends to warn drivers of branch points. Snow poles are installed along the left shoulder and median of roads as visual guidance and targets for snow removal work when visibility is poor due to blizzards.

Table 1: Guardrail Types, Their Main Characteristics, and Applicable Scenarios

Classification	Main Representative Type	Characteristics	Typical Applicable Scenarios
Rigid Guardrails	Concrete Guardrails	Not easily deformed; absorbs energy by forcing vehicles to climb; high protection level, but may cause significant impact on vehicles and occupants; convenient for maintenance.	Central medians; outer sides of bridges; sections with high proportion of large vehicles; sections requiring minimal deformation.
Semi-Rigid Guardrails	W-beam Guardrails, Box Beam Guardrails	Undergo some deformation upon impact, absorbing energy through deformation; good guidance; most common type; simple and convenient installation, relatively low cost.	Roadsides; central medians; curves; narrow medians (box beam).
Flexible Guardrails	Cable Guardrails	Possess significant deformation capacity, effectively absorbing collision energy; effective buffering, reducing vehicle damage; not suitable for sections with small curve radii.	Sections requiring large buffer space.
Combined Guardrails	Combined W-beam Steel Guardrails, Metal Beam-Column Guardrails	Combine advantages of multiple materials or structures; occupy less driving width, good sightlines, easy installation, relatively low cost; can meet aesthetic requirements; limited protection against super heavy vehicles.	Urban roads; bridges with special aesthetic requirements; steel structure bridges; road curves, intersections, entrances/exits affecting sight distance.

4. Typical Application Scenarios for Highway Guardrails

The installation of highway guardrails is based on a comprehensive assessment of road geometric characteristics, traffic operating conditions, environmental risks, and potential accident consequences. Their application scenarios cover multiple critical areas such as roadsides, central medians, and bridge and tunnel entrances/exits.

4.1 Principles and Scenarios for Roadside Guardrail Installation

The primary purpose of roadside guardrails is to prevent vehicles from running off the roadbed, especially in sections where severe consequences could result.

High Embankments and High Fill Sections: On Class II and above highways where the slope gradient and embankment height fall within specific shaded areas (Zones I and II), and on Class III and IV highways in Zone I, roadside guardrails must be installed to prevent vehicles from running off the roadbed and causing severe fall accidents. If a railway runs parallel within 15 meters of the roadside, and a vehicle leaving the road could fall onto the railway causing a secondary accident, guardrails must also be installed. This explicit requirement for upgrading guardrail protection levels based on road geometric features (such as sharp curves, steep slopes, high embankments) reflects a proactive risk management strategy. It indicates that guardrail design is not static but dynamically adjusted according to the inherent hazards of specific road sections, moving beyond a “one-size-fits-all” protection model towards a refined design based on risk assessment.
Case Study: The Gansu G212 and S306 Highway Safety Life Protection Project significantly improved safety on dangerous roadside sections by reinforcing, improving, or replacing existing protection facilities, effectively eliminating Class IV and V high-risk sections.
Sharp Curves, Continuous Sharp Curves, and Long Steep Downhill Sections: These sections are highly prone to vehicle loss of control due to complex alignment and difficulty in speed control. Therefore, the protection level of central median guardrails should be appropriately upgraded, and roadside guardrails should also be upgraded in high embankment sections.

Case Study: The Henan Jiyuan S240 Jideng Line highway project added reinforced concrete guardrails and W-beam guardrails in sharp curve and long steep downhill sections, supplemented by rumble strips and colored anti-skid pavement. This comprehensive application of multiple protective measures, such as colored anti-skid pavement, rumble strips, and the combination of rotating anti-collision barrel guardrails with traditional guardrails, demonstrates a multi-layered, integrated safety protection strategy. This indicates that optimal road safety relies on the synergistic effect of active (e.g., visual/auditory warnings) and passive (physical barriers) measures, rather than solely on guardrails themselves.
Case Study: On Xinjiang G315 highway, in sections with many curves and heavy vehicles, the original W-beam guardrails were replaced with RG-SA type rotating anti-collision barrel guardrails, and emergency parking strips were added, along with widening of curves, effectively decomposing vehicle impact force and preventing vehicles from penetrating the guardrail.

Sections Adjacent to Railways, Water Bodies, Dangerous Structures, or Sensitive Areas: On sections where a railway runs parallel within 15 meters of the roadside, and a vehicle leaving the road could fall onto the railway causing a secondary accident, or sections adjacent to reservoirs, oil depots, power stations, drinking water source protection areas, etc., requiring special protection, guardrails should be installed or their anti-collision level should be increased.
Exit Ramp Triangular Areas and Small Radius Curves: On expressways and Class I highways, guardrails should be installed in the triangular areas of exit ramps and on the outer side of small radius curves, as vehicles are prone to deviating from the lane in these areas, requiring protection.

4.2 Principles and Scenarios for Central Median Guardrail Installation

Central median guardrails are primarily used to separate opposing traffic lanes, prevent vehicles from crossing, and also serve traffic guidance and anti-glare functions.

Lane Separation and Traffic Guidance: The main purpose of central median guardrails is to separate traffic lanes in opposing (vertical) directions and guide the driver’s sight, ensuring orderly and safe traffic flow.
Central Median Openings: Central median opening guardrails must be installed at central median openings on highways to effectively close the openings, prevent vehicles from making U-turns or crossing indiscriminately, and ensure traffic safety. The width of the central median is an important consideration in guardrail design. This indicates that in designing guardrail systems, there is an optimization problem between space efficiency, cost-effectiveness, and safety performance. In urban or geographically constrained highway sections, the physical footprint of the guardrail system is a significant design constraint.
Anti-glare Applications: Anti-glare facilities, such as anti-glare nets, anti-glare panels, metal nets, or trees planted in the median (e.g., privet, azaleas), are installed on median guardrails to prevent glare from oncoming vehicle headlights from affecting drivers, ensuring safe and smooth night traffic. Anti-glare facilities as part of central median guardrails indicate that guardrail design considers the impact of environmental factors (such as oncoming headlight glare) on driver safety and can mitigate it through guardrails. This expands the functional scope of guardrails beyond mere physical collision protection.
Case Study: On the inner side of bridges, except for sections with anti-litter nets, anti-glare panels can be installed, typically made of green synthetic resin or fiberglass, with specific anti-glare angles to effectively block glare.

4.3 Application Scenarios for Bridge Guardrails

Bridge guardrails are installed to prevent vehicles from falling off bridges. Their design considerations are more complex, requiring comprehensive assessment of bridge height, environment below the bridge, traffic volume, and aesthetic requirements.

Preventing Vehicles from Falling Off Bridges: The primary role of bridge guardrails (such as parapet walls, i.e., reinforced concrete wall guardrails) is to prevent vehicles from leaving the bridge deck, especially on high bridges, sections with deep water below, or sections crossing railways or densely populated areas, which are high-risk locations.
Bridge Central Medians: For single-span bridges or bridges with only expansion joints between spans and sufficient deck strength, the central median guardrails should be designed referencing the principles for central median guardrails on roadbed sections.
Special Bridges:

Steel Structure Bridges and When Reducing Bridge Dead Load is Necessary: Metal beam-column guardrails are recommended due to their relatively lighter weight, which imposes less additional load on the bridge structure.
Bridges with Special Aesthetic Requirements or Urban Roads: Metal beam-column guardrails or combined guardrails are recommended to balance aesthetics and protective function. The selection criteria for bridge guardrails are multi-dimensional, including not only anti-collision performance but also structural load (e.g., choosing steel over concrete guardrails to reduce bridge self-weight) and aesthetic impact. This indicates that infrastructure design is a complex optimization problem that requires balancing safety, engineering constraints, and urban/environmental integration.
Sections Adjacent to or Crossing Areas with Special Protection Requirements: Such as main railways, reservoirs, oil depots, power stations, drinking water source protection areas, bridge guardrails should have special collision conditions determined and be specially designed, even increasing the protection level to HB, to cope with potentially catastrophic secondary accidents. For example, for bridges crossing large primary drinking water source protection areas, extra-large suspension bridges, cable-stayed bridges, and other cable-supported bridges, HB-level protection is recommended. This requirement for higher protection levels on bridges, especially those crossing sensitive areas , reflects a risk assessment framework that considers not only direct collision consequences but also potential catastrophic secondary impacts (e.g., train derailment, environmental pollution). This demonstrates a deep understanding of systemic risks in transportation infrastructure.

4.4 Application Scenarios for Tunnel Entrance/Exit Guardrails

Tunnel entrances and exits are special transition areas in the road environment, and guardrail installation here requires particular attention to driver visual adaptation and behavioral changes.

Transition and Connection with Roadbed/Bridge Guardrails: Tunnel entrances/exits are accident-prone areas. Guardrails here should be designed with transition sections to ensure a smooth transition in rigidity, height, cross-sectional form, and position with adjacent roadbed or bridge guardrails, avoiding new safety hazards. The mandatory requirement for “transition sections” and halving of post spacing at tunnel entrances/exits indicates that these areas are identified as high-accident locations due to sudden changes in driving environment (light, visibility, geometry) and driver behavior. This highlights the importance of considering psychological and perceptual factors in road design, not just physical barriers.

Case Study: Guardrails at tunnel entrances can be considered as a guardrail transition section from roadbed or bridge guardrails to the tunnel wall position, to achieve a smooth connection.
Case Study: Within 16 meters of the roadbed side of tunnel entrances/exits, the post spacing of W-beam steel guardrails should be halved to enhance the protective capability of this area against potential collisions.
Internal Safety Guidance in Tunnels: Reflective rings, solar LED flashing lights, etc., can be installed inside tunnels to clearly define the tunnel outline, increase brightness, enhance driving guidance, and simultaneously reduce lighting energy consumption, achieving dual benefits of safety and environmental protection.⁵ The practice of integrating advanced lighting and guidance systems (such as solar indicators, reflective rings) inside tunnels not only enhances safety but also considers energy efficiency and environmental benefits. This demonstrates a holistic engineering approach aimed at optimizing multiple objectives simultaneously, driving infrastructure towards “smart” development.

5. Special Application Scenarios for Urban Road Guardrails

The application of urban road guardrails differs from highways, focusing more on the safe isolation of pedestrians and non-motorized vehicles, maintenance of traffic order, and coordination with urban aesthetics.

5.1 Application of Pedestrian Guardrails

Pedestrian guardrails are crucial facilities for ensuring pedestrian safety on urban roads, designed to guide pedestrian behavior and prevent accidental falls.

Preventing Pedestrians from Crossing Motorized Vehicle Lanes: Pedestrian guardrails should be installed on roadsides where pedestrians need to be prevented from crossing motorized vehicle lanes, especially at intersection sidewalks, but should be interrupted at pedestrian crossings to facilitate pedestrian movement.
Preventing Pedestrians from Falling into Dangerous Areas: Pedestrian guardrails should be installed when there is a height difference between the sidewalk and the adjacent ground (exceeding 0.5 meters) or a risk of pedestrian falls, as well as on the outer side of bridge sidewalks.

Height Requirements: The clear height of road pedestrian guardrails should generally not be less than 1.10 meters, and not lower than 0.90 meters. When the open side of a bridge is a mixed pedestrian/non-motorized vehicle lane or a non-motorized vehicle lane, the clear height of the pedestrian guardrail should be greater than 1.40 meters to prevent riders from falling over the guardrail.
Structural Requirements: In areas with fall hazards, the clear distance between vertical members of railings should not exceed 0.11 meters, and structures with stepping surfaces should not be used. Measures to prevent flower pots from falling must also be in place to avoid secondary injuries. This detailed regulation on pedestrian guardrail height and vertical bar spacing, as well as the requirement to avoid climbable structures, reflects a refined consideration for pedestrian safety. This indicates that designers not only focus on preventing falls but also delve into preventing climbing, entrapment, and other secondary risks, especially for vulnerable groups like children, reflecting a deep understanding of pedestrian behavior patterns in urban public spaces and a preventive design mindset.
High Pedestrian Flow Areas: Pedestrian guardrails should be installed along the vehicle lanes in areas with high pedestrian traffic, such as stations, docks, pedestrian overpass and underpass entrances/exits, and commercial centers, to guide pedestrian flow and ensure safety.

5.2 Application of Non-Motorized Vehicle Lane Guardrails

Non-motorized vehicle lane guardrails are primarily used to separate motorized vehicles from non-motorized vehicles, and non-motorized vehicles from pedestrians, ensuring cycling safety.

Separating Motorized Vehicles from Non-Motorized Vehicles: Guardrails are used to isolate cyclists from motorized vehicles, preventing motorized vehicles from encroaching on non-motorized vehicle lanes and enhancing cycling safety.
Separating Non-Motorized Vehicles from Pedestrians: Where there is no parking lane next to the bicycle lane and adjacent vehicle speeds are low, guardrails can be installed to separate cyclists from pedestrians, while also preventing pedestrians from entering the bicycle lane, avoiding conflicts caused by mixed traffic.
Protection on Special Road Sections: In locations where anti-collision guardrails at curves, intersections, or entrances/exits affect driver’s sight distance, metal beam-column guardrails, combined guardrails, or W-beam guardrails with better transparency are recommended to balance safety and sightlines.
Design Principles: It is recommended to separate bicycle and pedestrian traffic through markings or dedicated paths, with a minimum design width of 3 meters for two-way bicycle lanes and 1.5 meters for pedestrian paths.

Near bus stops, bicycle lanes can be at the same height as sidewalks or streets, but should be raised to sidewalk height using ramps near stops to make it easier for pedestrians to access bus stop areas.
Intersections should be carefully designed to reduce vehicle speeds, control traffic entering the intersection, and set appropriate signage to minimize potential conflicts.

5.3 Guardrail Applications in Temporary Traffic Management

Temporary guardrails play an important role in construction areas, large-scale events, and emergency management, used for traffic guidance, area isolation, and safety protection.

Road Construction Work Zones:

Isolation Facilities: Conical traffic markers, guardrails, and other isolation facilities should be installed in urban road construction work sections to separate motorized vehicles, non-motorized vehicles, and pedestrian traffic, ensuring construction safety and traffic order.
Boundary Marking and Warning: Temporary guardrails can be used to mark boundaries, especially in long-term projects, replacing pedestrian guardrails and traffic cones to separate vehicle lanes from adjacent sidewalks or road construction areas. Temporary guardrails should be clearly marked, with red and white or other strongly contrasting reflective strips facing oncoming traffic, and warning lights installed at night to ensure visibility day and night. Water-filled barriers are often used in this scenario due to their stability and ease of movement.
Temporary Removal and Restoration: Construction safety protection facilities must not be arbitrarily removed, misappropriated, or abandoned; if temporary removal is necessary due to construction procedures, temporary protection facilities should be added, and immediately restored after the procedure is completed.
Large-Scale Public Events:

Crowd Guidance and Control: In large-scale public events, organizers should scientifically set up passenger entry and exit routes based on venue characteristics, adopting one-way circulation or no-return routes to guide passenger flow, reasonably divert, avoid intersecting flows, and prevent head-on crowding.²⁵ If necessary, organizers should rent guardrails, enclosures, and other safety facilities to enclose the venue or control personnel.
Safety Buffering and Emergency Response: Event organizers must establish safety buffer zones at the site to alleviate crowd pressure or evacuate personnel in emergencies. When crowd density is too high or may lead to stampedes, the circuit breaker mechanism should be immediately activated, the event terminated, and external cordon implemented, allowing only exits.
Traffic Diversion and Organization: During highway expansion, reconstruction, and maintenance projects, traffic diversion and organization work must be effectively carried out during guardrail renovation to ensure safe traffic operation. For large-scale events, if they may affect surrounding traffic and public order, organizers should formulate traffic guidance and order maintenance plans.

6. Conclusion

Highway guardrails, as a critical component of the road traffic safety system, have wide-ranging application scenarios and diverse functions, extending far beyond simple physical isolation. This report, through an in-depth analysis of guardrail applications on roadsides, central medians, bridges, tunnels, as well as urban roads and in temporary traffic management, reveals their core role in ensuring road safety, guiding traffic flow, and reducing accident losses.

The design and selection of guardrails are complex engineering decision-making processes that require comprehensive consideration of road geometric characteristics, traffic volume, vehicle composition, environmental factors, and potential accident consequences. For example, in high-risk sections such as sharp curves, steep slopes, and high embankments, the protection level of guardrails must be appropriately elevated, reflecting a dynamic design philosophy based on risk assessment. The selection of bridge guardrails must not only meet anti-collision performance but also consider structural load and aesthetic requirements, especially when crossing railways, reservoirs, and other sensitive areas, where their protection level needs to be significantly increased to cope with potentially systemic catastrophic secondary impacts. Guardrail design at tunnel entrances/exits emphasizes transition and visual guidance to adapt to drivers’ perceptual needs during changes in light and environment.

Furthermore, continuous innovation in guardrail technology, such as the application of combined guardrails and rotating anti-collision barrel guardrails, reflects the ongoing efforts in traffic engineering to enhance safety performance, optimize cost-effectiveness, and ensure environmental compatibility. These development trends indicate that future guardrail systems will be more intelligent, integrated, and better able to adapt to complex and changing traffic environments. Pedestrian guardrails and non-motorized vehicle lane guardrails on urban roads demonstrate refined protection for vulnerable road users (pedestrians, cyclists), building safer and more orderly urban traffic spaces through physical isolation and behavioral guidance.

In summary, the application scenarios of highway guardrails are multi-dimensional and systemic. Their design and implementation are not only technical challenges but also a profound embodiment of the “people-oriented, safety first” traffic philosophy. With the continuous growth of traffic demand and technological advancements, the role of guardrails in ensuring road safety will continue to evolve, moving towards more efficient, intelligent, and human-centered directions.