Assessment of road network structure, design standards and pavement condition within a road asset management system (RAMS): the case of Tajikistan

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1. Introduction

Road infrastructure is critical to the socioeconomic development of mountainous countries, where transport connectivity directly affects territorial cohesion [1, 2].

In the Republic of Tajikistan, the road network performs a dual function by supporting both domestic mobility and international transport flows. It provides essential links between regions with limited alternative transport modes and ensures the country’s integration into regional transport systems through the Central Asia Regional Economic Cooperation (CAREC) corridors and the Asian Highway network [1]. These routes play a strategic role in facilitating trade, transit traffic, and socioeconomic interaction with neighboring countries. Consequently, the performance and reliability of the road network have direct implications not only for national development but also for regional connectivity and economic cooperation [2].

A significant share of the road network in Tajikistan was constructed during the Soviet period under historical design assumptions for traffic intensity, vehicle composition, and economic conditions. Since then, traffic demand, axle loads, and the functional role of many roads have changed substantially, while financial resources for maintenance and rehabilitation have remained limited [3]. As a result, many roads currently operate beyond the assumptions underlying their original design.

This mismatch between design assumptions and actual operating conditions has led to accelerated pavement deterioration, lower travel speeds, and increased vehicle operating costs. These effects are particularly pronounced on national-level and local roads, which were designed for low traffic volumes but now serve important economic and social functions [4]. In mountainous terrain, the negative impacts of inadequate pavement structure are further amplified by geometric constraints and adverse climatic conditions.

Existing studies on road infrastructure in developing countries primarily focus on either pavement condition assessment or the economic evaluation of rehabilitation projects. At the same time, road design standards are often treated as static technical instruments, without explicit consideration of their long-term performance implications under changing traffic and budgetary constraints [5]. Comprehensive studies that integrate road network structure, design standards, pavement condition, and economic impacts within a unified analytical framework remain limited, particularly for mountainous countries such as Tajikistan.

This study aimed to assess the structure and condition of the road network of the Republic of Tajikistan and evaluate the limitations of traditional road design standards when applied without systematic asset management. The study seeks to: (i) analyze the road network by category and pavement surface type; (ii) review the fundamental provisions of road design standards; (iii) assess pavement condition across road classes; and (iv) examine the economic implications of pavement deterioration. Based on these findings, the paper substantiates the role of RAMS as a fundamental instrument for evidence-based maintenance and rehabilitation planning under limited financial resources [3, 4].

2. Road network structure

The public road network of the Republic of Tajikistan is regulated by the Law on Roads and Road Activities, which classifies roads into international, national, and local categories according to their functional role [6]. International roads provide cross-border connectivity and form part of the CAREC corridors and the Asian Highway network, while national roads connect major cities and regional centers. Local roads ensure access to rural settlements and intra-district mobility, and constitute the largest share of the network [7].

The total length of the road network in Tajikistan is approximately 26,600 km. Of this, 14,339 km are public roads managed by the Ministry of Transport (Table 1), whereas the remaining roads are industrial and access roads managed by other government agencies or private enterprises [1, 7]. The structure of the public road network is highly unbalanced in terms of functional hierarchy: local roads account for about 61.9% of the total public road length, whereas international and national roads represent 23.3% and 14.8%, respectively [7].

Table 1. Road network by category and surface type (km)

Source: Government of Tajikistan, Ministry of Transport

From the perspective of pavement surface type, the road network exhibits substantial heterogeneity. Approximately 70% of public roads are paved; however, only about one-third of the total network length is surfaced with asphalt concrete. The remaining paved roads predominantly consist of bituminous gravel and plain gravel surfaces, whereas unpaved roads are mainly concentrated within the local road category [1]. This distribution reflects historical investment priorities that favored international corridors, whereas lower-category roads were built with less durable pavement structures.

Asphalt concrete surfaces are most prevalent on international roads, where they account for more than half of the total length. National roads also exhibit a relatively balanced distribution between asphalt and non-asphalt surfaces. In contrast, local roads are dominated by bituminous gravel, gravel, and unpaved sections, which significantly reduces their structural capacity and resistance to traffic loads [3].

The predominance of lower-category roads with non-asphalt surfaces has important implications for network performance and sustainability. Gravel and unpaved roads are more sensitive to traffic growth, increased axle load, and climatic conditions, leading to faster deterioration and higher maintenance requirements. In mountainous regions, these effects are further intensified by steep gradients, freeze–thaw cycles, and drainage constraints [2, 4].

Overall, the structural characteristics of the road network highlight a fundamental challenge for road management in Tajikistan. While international roads benefit from higher technical standards and better pavement types, the majority of the network consists of local roads that have limited durability. This imbalance underscores the need for a systematic approach to maintenance and investment prioritization that accounts for network structure, pavement type, and long-term performance within a road asset management framework [3, 5].

3. Road design standards

Road design standards in the Republic of Tajikistan define the technical parameters of public roads and provide the basis for planning, construction, and rehabilitation activities. These standards classify roads into five categories (I–V) according to average daily traffic intensity, design speed, number of lanes, and key geometric characteristics, such as lane width, roadway width, and maximum longitudinal slope [8].

The classification system reflects a hierarchical approach to road network development. Higher-category roads (categories I–II) are designed to accommodate high traffic volumes, higher design speeds, and greater proportions of heavy vehicles, while lower-category roads (categories IV–V) are intended for limited traffic intensity and reduced operating speeds. These assumptions directly influence pavement structure, geometric design, and expected service life [4].

Table 2 summarizes the principal design parameters for each road category, including traffic thresholds, design speed ranges, and geometric dimensions. The values presented in the table show a consistent decrease in design speed from category I roads to category V roads, along with a corresponding reduction in roadway width and structural capacity. This differentiation ensures cost effectiveness at the design stage by matching road standards to anticipated traffic demand [8].

Table 2. Road Design Standards by Category

Source: Russian Construction Codes and Regulations (SNiP 02.05-85)

However, the design standards are inherently static and are based on traffic and economic conditions prevailing at the time of project preparation. They do not explicitly account for long-term traffic growth, changes in freight patterns, or functional upgrading of roads over time. As a result, roads initially designed for low traffic volumes may subsequently experience loads that exceed their original design assumptions, particularly in regions where alternative routes are limited [3].

In mountainous environments, the limitations of static design standards become especially pronounced. Steep gradients, sharp horizontal curves, and climatic factors such as freeze–thaw cycles impose additional stresses on pavement structures and reduce their effective service life. While design standards allow for higher longitudinal slopes for lower-category roads, such allowances may accelerate deterioration when combined with increasing traffic and insufficient maintenance [2, 4].

The analysis of design standards in the context of actual road performance indicates that compliance with regulatory design parameters alone does not guarantee sustainable operation of the road network. Without systematic monitoring and timely maintenance intervention, roads designed according to lower-category standards are more likely to deteriorate rapidly, leading to higher life-cycle costs and reduced service quality. This highlights the need to complement traditional design standards with performance-based planning tools and asset management principles [3, 5].

4. Pavement Condition

The technical condition of the public road network in the Republic of Tajikistan is assessed using qualitative condition classes commonly used in international practice: good, fair, and poor. These classes reflect the overall state of pavement surface integrity, roughness, and serviceability, and are widely used for network-level condition assessment and maintenance planning [3, 4, 9, 10].

According to the most recent data from the Ministry of Transport, a large proportion of the public road network is currently in unsatisfactory condition. Table 3 shows that approximately 56% of public roads are classified as poor, whereas only 12% are classified as good. This distribution indicates a predominance of deferred maintenance and highlights the cumulative effects of long-term underinvestment in road preservation [7].

Table 3. Estimated road conditions (%)

Source: Government of Tajikistan, Ministry of Transport

Significant differences in pavement condition are observed across road classes. International roads demonstrate relatively better performance, with more than half of their length classified as good or fair. This reflects higher design standards, greater structural capacity, and prioritization of international corridors within national investment programs supported by development partners [1]. In contrast, national and local roads exhibit considerably worse conditions, with 59% and 66%, respectively, classified as poor [7].

Compared with the assumptions embedded in road design standards, the observed pavement condition reveals a systematic mismatch between regulatory design parameters and actual operating conditions. Roads designed for low traffic intensity and limited heavy vehicle presence are currently subject to higher traffic volumes, increased axle loads, and more intensive use than originally anticipated [4]. This mismatch accelerates pavement deterioration and shortens service life, especially where routine and periodic maintenance is insufficient.

In mountainous regions, pavement degradation is further intensified by environmental factors such as steep gradients, temperature fluctuations, freeze–thaw cycles, and drainage constraints. These conditions increase mechanical and environmental stresses on pavement structures and exacerbate the consequences of delayed maintenance interventions [2]. Consequently, pavement condition in mountainous areas deteriorates faster than standard design assumptions would predict.

Overall, the current state of pavement condition across the road network underscores the need to go beyond purely regulatory approaches to road management. Systematic condition monitoring and performance-based planning are essential to identify priority sections, prevent further network degradation, and reduce long-term economic losses resulting from poor road condition [3, 5].

5. Economic impacts

5.1. Vehicle operating costs

Road condition directly and measurably affects transport costs and overall economic efficiency. Pavement deterioration leads to increased vehicle operating costs (VOC), reduced travel speeds, and lower reliability of transport services. These effects are particularly significant in countries with mountainous terrain, where geometric constraints and climatic factors amplify the consequences of poor road condition [3, 4].

Vehicle operating costs include fuel consumption, tire wear, maintenance and repair costs, depreciation, and travel time. Numerous empirical studies have demonstrated that VOC are highly sensitive to pavement roughness and surface type. On gravel and unpaved roads, vehicle operating costs may be 1.5–2.0 times higher than on asphalt concrete roads under comparable traffic conditions [11–13].

In Tajikistan, a large proportion of local roads are surfaced with gravel or remain unpaved, while a significant share of the network is classified as in poor condition. As a result, road users incur substantial additional costs that are not directly reflected in road agency budgets but are borne by households, businesses, and transport operators. These hidden costs constitute a significant economic burden, particularly for rural communities that depend on local roads for access to markets and services [1].

5.2. Speed reduction and travel time losses

Poor pavement condition leads to reduced operating speeds and increased travel time. Field observations indicate that, on many road sections, average travel speed does not exceed 30 km/h, even where higher design speeds are specified. Speed reductions increase fuel consumption per trip, reduce vehicle productivity, and raise logistics costs, particularly for freight transport [2].

For passenger transport, longer travel times negatively affect access to employment, education, healthcare, and administrative services. In mountainous regions with limited route alternatives, these impacts are especially pronounced, as users often have no viable detours to avoid deteriorated road sections [5].

5.3. Accessibility and socioeconomic effects

Beyond direct transport costs, pavement deterioration affects regional accessibility and socioeconomic development. Poor road condition can lead to temporary or seasonal isolation of settlements, particularly during adverse weather conditions. Reduced accessibility constrains economic activity, limits market integration, and increases regional disparities [13].

In Tajikistan, where a large share of the population resides in rural and mountainous areas, road accessibility plays a critical role in ensuring social inclusion and economic resilience. Consequently, the economic impacts of road deterioration extend beyond transport efficiency and encompass broader social and developmental dimensions [1, 13].

5.4. Implications for economic efficiency

Traditional road management approaches often prioritize short-term budget constraints over long-term economic efficiency. However, delayed maintenance and rehabilitation typically result in higher total costs due to accelerated pavement deterioration and increased user costs. International experience shows that timely preventive maintenance yields significantly higher economic returns than deferred rehabilitation, particularly on lower-category roads [3, 12].

Integrating economic impact assessment into road management decisions enables road agencies to identify interventions that minimize total social costs rather than focusing solely on agency expenditures. This perspective is essential for achieving sustainable performance of the road network under limited financial resources.

5.5. Summary of economic impacts

The analysis confirms that poor pavement condition imposes substantial economic burdens through higher vehicle operating costs, lower travel speeds, and reduced accessibility. In the context of Tajikistan, these impacts are amplified by the predominance of lower-category roads and the challenging mountainous errain. Addressing these issues requires a shift toward systematic, performance-based planning that explicitly accounts for economic efficiency in maintenance and investment prioritization [3, 4].

6. Limitations of traditional road management approaches

6.1. Limitations of traditional road management approaches

Traditional road management in many developing and transition economies is largely reactive and project-oriented. Maintenance and rehabilitation decisions are often based on visual inspections, short-term budget availability, and urgent repair needs rather than on systematic performance assessment and long-term planning. Such approaches tend to focus on restoring damaged sections without adequately considering life-cycle costs and user-related economic impacts [3].

In Tajikistan, this reactive model is further constrained by limited financial resources and the large share of roads with low structural capacity. As shown in previous sections, many roads operate beyond their original design assumptions, which accelerates deterioration and increases vehicle operating costs. Without an integrated framework for prioritizing interventions, available funds are often allocated in a way that does not minimize total social costs [5].

6.2. Core principles and functions of RAMS

A Road Asset Management System provides a structured and systematic approach to managing road infrastructure throughout its entire life cycle. RAMS integrates technical, traffic, and economic information to support evidence-based decision-making. Core functions of RAMS typically include [14–16]:

– systematic collection and management of data on pavement condition, traffic volumes, and asset characteristics;

– performance assessment using technical indicators such as roughness, surface distress, and structural capacity;

– forecasting of pavement deterioration under alternative maintenance and rehabilitation scenarios;

– evaluation of life-cycle costs and user-related economic impacts;

– prioritization of interventions under budgetary constraints.

By combining these functions, RAMS enables a shift from short-term, reactive decision-making toward long-term, performance-based planning [3, 4].

6.3. Integration of technical and economic indicators

A key advantage of RAMS is its ability to integrate technical condition indicators with economic performance measures. Pavement condition indicators are directly linked to vehicle operating costs, travel time, and accessibility impacts, allowing road agencies to quantify the economic consequences of different maintenance strategies.

Such integration enables comparison of alternative intervention options based on their total life-cycle costs rather than on initial construction or rehabilitation costs alone. International experience shows that timely preventive maintenance often yields significantly higher economic returns than delayed rehabilitation, especially on lower-category roads with limited structural capacity [11, 12, 17].

6.4. International experience and applicability to Tajikistan

International development institutions and road agencies widely recommend RAMS-based approaches as best practices for sustainable road network management. Frameworks such as the Highway Development and Management Model (HDM-4) and guidelines from international organizations provide methodological support for implementing asset management principles under diverse conditions [3, 4].

For Tajikistan, the adoption of RAMS is particularly relevant due to the combination of mountainous terrain, heterogeneous road conditions, and constrained budgets. A system-oriented approach allows decision-makers to balance investments between international corridors, national roads, and local roads based on objective performance and economic efficiency criteria rather than on ad hoc considerations [1].

6.5. Institutional and strategic implications

The effective implementation of RAMS requires not only technical tools but also institutional capacity and organizational commitment. This includes establishing standardized data collection procedures, developing analytical skills within road agencies, and embedding asset management principles into planning, budgeting, and investment decision-making processes.

From a strategic perspective, RAMS enhances transparency and accountability by providing a clear rationale for prioritization of maintenance and rehabilitation projects. Over time, this contributes to more efficient use of public funds, improved service quality, and greater sustainability of the road network [3, 5, 17, 18].

Overall, road asset management systems offer a comprehensive solution to the limitations of traditional road management approaches. By integrating technical condition assessment with economic impact analysis, RAMS supports evidence-based prioritization of interventions and enables sustainable road network performance under limited financial resources.

7. Conclusions

This study provides an integrated assessment of the Tajikistan’s road network, focusing on administrative classification, pavement condition, and design parameters within the RAMS framework. The analysis confirms that the structural characteristics of the road network, particularly the predominance of local roads with lower-rade surfaces, are decisive factors in pavement deterioration in mountainous terrain.

The results demonstrate that local roads account for the largest share of the country’s road network and exhibit the highest proportion of pavements rated as poor. In contrast, international and national roads show relatively better performance due to higher design standards and maintenance priorities. This imbalance highlights the limitations of traditional maintenance approaches based solely on regulatory design requirements and reactive interventions [2].

The findings underline the need to transit to a data-driven RAMS approach that integrates road classification, pavement condition indicators, and functional importance of road links. Such integration enables objective prioritization of maintenance and rehabilitation activities, particularly under budget constraints. The analysis confirms that systematic assessment of pavement condition by road class offers a practical basis for optimizing maintenance planning and improving long-term network performance [11, 12, 17, 18]

From a policy perspective, the proposed approach supports the development of more efficient transport strategies for mountainous countries, where geographical constraints and climate-induced deterioration significantly affect infrastructure sustainability. The experience of the Republic of Tajikistan demonstrates that RAMS implementation can serve as an effective tool to improve transparency, consistency, and economic efficiency of road management decisions [1, 3].

Overall, the results of this study contribute to applied research in road infrastructure management in mountainous regions and provide transferable insights for other developing countries facing similar challenges. Future research should focus on incorporating performance-based indicators, such as roughness and vehicle operating costs, into RAMS frameworks to further enhance decision-making and investment efficiency [2, 9].

Автор заявляет, что настоящая статья не содержит каких-либо исследований с участием людей в качестве объектов исследований.

The author declares that this article does not contain any research involving humans as research subjects.

About the authors

Sukhrob B. Mirzozoda

Author for correspondence.
Email: sukhrob63@mail.ru
ORCID iD: 0000-0002-9817-3633

Cand. Sci. (Engineering), associate professor

References

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