POSSIBILITIES FOR THE IMPROVEMENT OF THE QUALITY OF DESIGN SOLUTIONS IN THE GRAVEL ROAD RECONSTRUCTION PROJECTS

This article provides a summary of the author’s PhD thesis on possibilities for the improvement of the quality of design solutions in gravel road reconstruction projects. The thesis includes five chapters: analysis of the Gravel Road Network in Lithuania and analysis of the gravel roads development; analysis of the road design standards of the Republic of Lithuania compared to other countries; methodology of experimental investigations; results of the investigations; and conclusions based on the investigation results. In this work, the author proposes a new road design methodology in which road alignment is characterized as a sequence of successive interrelated elements, including traffic safety criteria. The author concludes that present regulations for road design in the Republic of Lithuania are inaccurate and deficient and should not be used for road reconstruction projects, particularly on gravel roads. Recommended corrections and supplements to these regulations are presented. The original thesis, in Lithuanian, is available upon request from the author.


State of the problem
Despite large investments in the development of the road network of national signifi cance and the improvement of traffi c safety, the number of accidents on the roads of the Republic of Lithuania in the last years remained one of the largest in the European Union (EU). Th is allows to make an assumption that not all the improvements of the road network are suffi ciently eff ective, including design solutions of the road reconstruction projects. A great concern is caused by the design solutions in the gravel road reconstruction projects which could be unsuitable in terms of traffi c safety, since it is common practice in Lithuania to design the planned road axis of the gravel road to be reconstructed with the min deviation from the existing road axis. Th e main motivation for this gravel road reconstruction practice is to reduce the cost of reconstruction works at the expense of taking of land for the planned right-ofway. Another important reason for making the currently used practice of the reconstruction of lower-category roads, including gravel roads, is the liberal road design standards of the Republic of Lithuania allowing to rather freely interpreting observance of their requirements.
Topicality of the work. Motivation for the gravel road reconstruction practice used in Lithuania in the last 10 years can possibly be insuffi ciently justifi ed. Besides, in the road design standards of the Republic of Lithuania the main requirements for the solutions of road alignment had been essentially changing, therefore, the current design standards can contain certain inaccuracies which must be corrected. Also, it is necessary to supplement the road design standards with the new requirements ensuring the solutions of a smooth and safe road alignment.
Th e object of research -regularities for the design of road alignment, design solutions in the gravel road reconstruction projects and their links with the requirements of road design standards.
Aim and tasks of the work. Th e aim of this workto determine regularities for the design of road alignment, their links with the requirements of road design standards and to suggest the methods for improving the quality of design solutions.
Th e following tasks were solved to achieve the aim of the work: to make analysis of the requirements of road design  standards regulating the solutions of road alignment and to give suggestions for the improvement of these regulations; to evaluate the quality of the existing road align- ment and the volume of possible correction of horizontal and vertical alignment of the gravel road sections to be reconstructed; to carry out investigations of accident rate of the re- constructed gravel road sections by comparing the accident rate before and aft er reconstruction; to determine the quality of design solutions of road  alignment in the gravel road reconstruction projects; to identify the volume of taking of land for the  right-of-way in case if the gravel road reconstruction projects had been prepared according to the requirements of design standards; to evaluate if the current practice in Lithuania when  reconstructing gravel roads to use the least deviation from the existing road axis is justifi ed. Methodology of research. In order to determine possible inaccuracies in the requirements of road design standards of the Republic of Lithuania regulating the solutions of road alignment and to give suggestions for correcting and supplementing these requirements the method of comparative analysis was used for the investigations of this work. 3 experimental investigations were carried out using methodology developed during the preparation of this work, i.e.: for the investigation of horizontal alignment of  gravel roads; for the investigation of vertical alignment of gravel  roads; for the prediction of the volume of taking of land  for public needs. Statistical methods were used for the investigations of the accident rate of gravel roads before and aft er reconstruction. For experimental investigations to defi ne the quality of design solutions in the gravel road reconstruction projects the methodology of traffi c safety criteria was applied.
Scientifi c novelty. Th e following results new to the science of civil engineering were obtained in the course of preparation of the dissertation: a new design methodology adjusted to the improve- ment of requirements of road design standards regulating the solutions of road alignment and to the improvement of the quality of design solutions in the road reconstruction projects, intended for studying road alignment as a succession of interrelated elements; geometrical parameters of the existing alignment  of gravel roads in the road network of national signifi cance of the Republic of Lithuania; determination of the quality of design solutions of  road alignment in the gravel road reconstruction projects; changes in the accident rate of gravel roads before  and aft er reconstruction. Practical value. Th e practical application of the results of investigations carried out within the framework of this work would enable to improve the quality of design solutions when preparing reconstruction projects for the lower-category rural roads: road design standards of the Republic of Lithuania  would be improved and would ensure design solutions for a geometrically smooth and safe road alignment; the use of methodology of traffi c safety criteria  would enable to identify and eliminate the poten-tially dangerous road sections early in the stage of their design. Defended propositions. It is necessary to improve the requirements of road design standards of the Republic of Lithuania based on regularities for the design of road alignment and the quality of design solutions in the road reconstruction projects.
When preparing the gravel road reconstruction projects a possibility of deviation from the existing road axis shall not be restricted.

Gravel road network and its development in the Republic of Lithuania and analysis of its development
A large part of the road network of national signifi cance of Lithuania is still made of gravel roads. In 1998 the Gravel Roads Paving Programme (hereaft er Programme) was started to be implemented the main objectives of which is to increase the density of road network with the improved pavement and to eliminate the current disproportions in the development of road network. According a data of the Lithuanian Road Administration under the Ministry of Transport and Communications of the Republic of Lithuania during implementation of the Programme in 1998-2009 the part of gravel roads in the road network of national signifi cance was decreased from 49.1% to 35.9%, and until the year 2015 it is aimed to decrease this part to 30%.
However, the practice of implementing the Programme revealed serious defi ciencies, the most important of which -hastiness in the programme implementation having the aim that the period from the beginning of design works to the end of reconstruction works would last no more than 1-2 years. Such a short period of time is possible in those cases when the alignment of the existing gravel road is not being corrected or the correction of alignment is restricted by the requirement that the planned roadbed would go into the existing right-of-way. Such design solutions of road alignment are supposed to be acceptable in the gravel road reconstruction projects and this became a common practice of implementing the Programme. Th is practice of laying the improved pavement on gravel roads is not applied in the neighbouring Baltic countries.
Th e reasoning and consequences of the current practice of implementing the Programme has not been objectively determined yet. Since accident indices in Lithuania remain one of the worst in the EU the assurance of road traffi c safety is one of the most important tasks of presentday. Th erefore, it is very important to avoid the worsening of traffi c conditions in the reconstructed gravel roads.

Analysis of the road design standards of the Republic of Lithuania and foreign countries
Th e aim of investigation -to compare the requirements of road design standards regulating the solutions of road alignment of various countries, to determine possible inaccuracies in the design standards of the Republic of Lithuania and to give recommendations for the correction of inaccuracies determined and for the improvement of design standards .
It was determined during the comparison of requirements of road design standards of the Republic of Lithuania and other countries that some requirements for the solutions of road alignment in Lithuania are signifi cantly diff erent from the analogical requirements in the design standards of other countries: only two speeds are determined for design needs - design speed V d and permissible speed V p ; there is no concept of the speed  V 85 characterizing a real driving speed of vehicles; no indication is given on the methodology based  on which the V d is determined; the min radii of horizontal and vertical curves are  obviously diff erent from the average used in other countries. Th e min radii of horizontal curves defi ned in the current road design standards of the Republic of Lithuania are higher than those defi ned in the standards of other countries, whereas, the radii of humps are apparently lower. Th e least deviation from the average of foreign countries is represented by the radii of transverse depressions. Th erefore, there are some doubts if the radii of horizontal and vertical curves in the current road design standards of the Republic of Lithuania are properly justifi ed (Gintalas et. al. 2007a).
Th e radii of horizontal and vertical curves were checked by the formulas presented in the literature sources, making an assumption that pavement properties in Lithuania correspond to the average of West European countries and USA -the values of tangential friction factor f T and side friction factor f R used in the formulas were calculated by overall regression equations that were made during the investigations carried out in the above mentioned countries (Бабков et al. 1970;Бабков 1983;Кудрявцев et al. 1973;Xавкин et al. 1966;Lamm 1984;Lamm et al. 1989;Lamm et al. 1990b;Lamm et al. 1992;Lamm et al. 1995a;Lamm 1995c;Lamm et al. 1996).
It was determined that in the road design standards of the Republic of Lithuania: the values of the radii of horizontal curves are set  with a large reserve, and this reserve is unjustifi ed; the values of the radii of vertical curves are incon- sistent with the visibility requirements and, in contrast to the horizontal curves, are too low or having no reserve. When preparing road construction or reconstruction projects it is very important to not only properly design separate elements of road alignment but also to properly combine them in-between. In order to ensure the solutions of smooth and sage road alignment the following requirements are given in the road design standards: for the compatibility of the radii of adjacent hori- zontal curves; for the compatibility of the radii of horizontal curves  and the lengths of tangents between the curves; for a geometrical smoothness of the whole road  alignment. To properly select the radii of adjacent horizontal curves usually the detail nomograms of radii compatibil-ity are presented which are almost the same in the road design standards of various countries. Requirements for the compatibility of the radii of horizontal curves and the lengths of tangents between the curves are usually not so comprehensive as for the compatibility of the radii of adjacent horizontal curves, and this is a certain defi ciency of design standards. Another defi ciency of the road design standards of the Republic of Lithuania is that the smoothness of the whole road alignment is only mentioned and no recommendations are given on how to achieve it.
This work describes a new road design methodology according to which road alignment is studded as a sequence of successive interrelated elements. This methodology is based on the concepts of Curvature Change Rate (CCR S ) and traffic safety criteria (Lamm et al. 2007;Lamm et al. 1971b;Lamm et al. 1990b;Thoma 1994).
Th e traffi c safety criteria are as follows: criterion I -stability of the  V d ; criterion II -stability of the  V 85; criterion III -dynamic stability on horizontal  curves. Having summed up the values of traffi c safety criteria and having calculated their average, the design level of traffi c safety module is identifi ed .
Methodology based on the traffi c safety criteria allows us: to properly select the  V d according to the calculated values of V 85 for the whole road section to be reconstructed or for its separate segments; to properly combine between each other the ele- ments of road -horizontal curves and tangents between them. Using this methodology the problem of modelling the V 85 in horizontal curves and the tangent between them was solved in this work (Fig. 1), the aim of which -to give detail recommendations for the compatibility of the elements of horizontal alignment (Lamm et al. 1993b;Lamm et al. 1995a;Lamm et al. 1995b).
Problem formulation -to fi nd out the max tangent length TL when the following is given: the radii of horizontal curves  R 1 , R 2 ; the permissible diff erence Δ  V 85 between the V 85 in horizontal curves and the tangent. Using the tools of computer-aided design system the modelling of the existing vertical alignment was carried out in the following order: development of a digital model of location;  design of horizontal alignment without deviation  from the existing axis; design of vertical alignment without deviation from  the existing heights. Th e main objective of the investigation of accident rate of gravel roads is to compare accident indices on the reconstructed gravel road sections before and aft er their reconstruction (Elvik 2009;Gintalas et al. 2008;Hauer 2005;Kapski et al. 2007Kapski et al. , 2008Peltola 2000;Ratkevičiūtė et al. 2006;. Investigation of accident rate of gravel roads was carried out in the following stages: collection of accident data on the reconstructed  gravel road sections; comparison of accident indices before and aft er re- construction; economic evaluation of accident losses.  Th e tables of recommended max tangents between the small-radius (100-500 m) horizontal curves were worked out based on (4) formula.

Methodology of experimental investigations
Th e chapter describes methodology developed or adjusted during the preparation of this work for the following experimental investigations: for the investigation of horizontal alignment of  gravel roads; for the investigation of vertical alignment of gravel  roads; for the investigation of accident rate of gravel  roads; for the determination of the quality of design solu- tions in the gravel road reconstruction projects; for the prediction of taking of land for the right- of-way. Investigation of horizontal alignment was carried out in the following stages (Gintalas et al. 2005b;Gintalas et al. 2007a;Gintalas et al. 2007b;Gintalas et al. 2008;Vitkienė et al. 2008): vectorization of road alignment in the digital orto- photographical map ORT10; separation of a linear object, representing the road  axis, into the tangents and circular arcs, determination of the position of turning points (vertices of the angles) of road alignment and identifi cation of coordinates; (2) tangent length  . ( By joining (1)-(3) formulas together the fi nal expression of tangent length is obtained (4) . .
For the analysis of the quality of design solutions in the gravel road reconstruction projects the following investigations were implemented: evaluation of the correspondence of the solutions  of horizontal alignment to the requirements of design standards; identifi cation of potentially dangerous road seg- ments based on the methodology of traffi c safety criteria. Th e aim of evaluating the correspondence of the solutions of horizontal alignment to the requirements of design standards was to determine what part of horizontal curves is designed improperly. Th e following horizontal curves were attributed to the improperly designed ones: curves the radii of which are lower that it is re- quired by the design standards valid at the time of project preparation; curves with the improperly designed transition  curves. When identifying potentially dangerous segments that may appear in the implemented gravel road reconstruction projects each section under investigation was divided into segments in a way that one segment correspond to one element of horizontal alignment. Investigation was carried out in the following stages: identifi cation of dangerous segments on the sec- tions under investigation; collection of accident data on the sections under  investigation; determination of statistical relationship between  the accidents on the sections under investigation and the identifi ed dangerous segments on them. Identifi cation of dangerous segments on the road sections under investigation was carried out in the following order: determination of the average  CCR S ; determination of the speed  V 85 using the overall world-wide regression equations; analysis of the planned road alignment by defi n- ing for each segment a design level of traffi c safety module; identifi cation of a dangerous road segment if the  value of a dangerous design level of traffi c safety module is obtained; dangerous segments were identifi ed for both traffi c  directions. When reconstructing roads the following situations may occur: correction of horizontal alignment (position of the  road axis is changed); increase in the width of right-of-way.  In both cases the taking of land for the right-of-way is necessary by the established order of the Law on Territorial Planning.
Th e objectives of predicting the volume of taking of land for the right-of-way are as follows: to determine the volume of possible taking of land  for the right-of-way in case when the detail designs for the gravel road reconstruction are prepared according to the requirements of design standards; to determine possible costs of taking of land and  their ratio to the cost of road reconstruction works. Investigation of the volume of possible taking of land for the right-of-way was implemented in the following stages: design of one of the possible alternatives for the  planned road alignment with the tools of computer-aided design system; determination of land areas to be taken for the right- of-way according to the deviation of the planned road axis in respect of the existing road axis; identifi cation of the number of land plots the lim- its of which have to be corrected due to the deviation of the road axis based on the database of SE Registrų centras (Centre of Registers); determination of possible costs of taking of land for  the right-of-way; analysis of results. 

Results of experimental investigations
Investigations of horizontal and vertical alignment were carried out on the planned to be reconstructed gravel roads under the supervision of SE Telšių regiono keliai. Investigations of horizontal alignment were implemented on 24 sections with the total length of 111.90 km. Investigations of vertical alignment of gravel roads were carried out on 21 road section with the total length of 95.50 km. Investigation results showed that the quality of the existing road alignment of gravel roads is poor -56-78% of horizontal curves (making 19-27% of the length of investigated sections) and 68-89% of vertical curves (making 25-36% of the length of investigated sections) should be corrected (Fig. 2).
Investigation of accident rate was implemented on 53 reconstructed gravel road sections in the Western Lithuania, the total length of which -204.88 km. On those sections in the period 1998-2006 199 fatal and injury accidents were recorded, 76 of which -before reconstruction, 123 -aft er reconstruction. Besides, aft er reconstruction 2 high-accident sections and 2 black spots were recorded on the gravel roads under investigation. Investigation results showed that: aft er reconstruction the average density of fatal and  injury accidents on the sections of investigation sample has increased twice -from 0.06 to 0.13 accidents per year; accident costs per 1 km of the reconstructed grav- el road, in the investigated sections were about 93 000 Lt/year (based on 2006 prices). A more comprehensive analysis of accident rate was carried out on the gravel roads under the supervision of SE Telšių regiono keliai by analyzing both types of accidentsfatal and injury as well as damage-only accidents (Fig. 3). It was determined that aft er reconstruction of the gravel roads under the supervision of SE Telšių regiono keliai the density of both types of accidents has increased 2.7 times.
Evaluation of the correspondence of the solutions of horizontal alignment to the requirements of design standards was carried out on the sections of the accident rate investigation sample -53 detail designs of gravel road reconstruction, prepared for the road sections with the total length of 204.88 km, were studied. It was determined that 14 gravel road reconstruction projects (26.4% of all the projects) were prepared without giving any solutions for the horizontal alignment. 39 gravel road reconstruction projects (73.6% of all the projects) were fully completed, however, the quality of the solutions of horizontal alignment was poor -on the average 34.9% of horizontal curves were designed improperly.
Investigation for identifying the potentially dangerous segments was implemented on 8 gravel road sections with the total length of 39.26 km. For this investigation the detail designs of gravel road reconstruction were also used. It was determined that at least 5% of the total length of investigated reconstructed gravel road sections is made of the potentially dangerous segments, besides, there is a sta-tistical correlation between the identifi ed dangerous road segments and the accidents on them. When identifying the potentially dangerous segments it was also determined that in all detail designs of investigation sample the V d was selected improperly -based on the design standards, valid at the time of their preparation, the value of V d = 60 km/h was set, whereas, it had to be set as V d = 70-90 km/h. Th e forecast of the volume of taking of land for the right-of-way shows that: when taking land for the right-of-way the predicted  costs per one gravel road section to be reconstructed average to 59 000 Lt of the calculated cost of laying asphalt pavement; the higher the length of the section to be recon- structed the lower ratio would be between the costs of taking of land for the right-of-way and the calculated cost of laying asphalt pavement (Fig. 4). It was determined that the ratio between the costs of taking of land for the right-of-way and the calculated cost of laying asphalt pavement is also related to the length where S -ratio between the total costs of taking of land for the right-of-way and the calculated cost of laying asphalt concrete pavement, %; L -length of the road section to be reconstructed, km; m, n -coeffi cients of exponential function.

Generalization of investigation results
Th is chapter gives an overview of results of all investigations carried out during the preparation of this dissertation: detail recommendations for improving the road  design standards of the Republic of Lithuania regulating the solutions of road alignment; results of all experimental investigations imple- mented.

General conclusions
When analyzing regularities of the design solutions of road alignment and their links with the regulations of road design standards it was determined that the current regulations of road design standards of the Republic of Lithuania have certain inaccuracies and defi ciencies. A further use of these requirements for designing road alignment will result in the preparation of low-quality road reconstruction projects in terms of traffi c safety, especially on the roads of lower categories.
Investigations of horizontal and vertical alignment of gravel roads show that the quality of the existing alignment of gravel roads is poor -56-78% of horizontal curves and 68-87% of vertical curves should be corrected.
In the result of comparative investigations of accident rate of the reconstructed road sections it was determined that: aft er reconstruction the accident rate (accident  density) is increased up to 3 times; accident costs per 1 km of the reconstructed grav- el road make about 93 000 Lt/year (based on 2006 prices). Based on the analysis of the quality of design solutions in the gravel road reconstruction projects, it could be stated that: the values of design speed  V d are selected improperly; requirements for the solutions of horizontal align- ment of roads are not observed -approximately one third of horizontal curves are designed incorrectly; the elements of horizontal alignment are incompat- ible -at least 5% of the total length of the reconstructed road sections are comprised of potentially dangerous segments.
When taking land for the right-of-way the predicted expenditures per one gravel road section to be reconstructed are averaged to 59 000 Lt (based on 2006 prices). Th ey make only a small part of the calculated cost of road reconstruction works, and this part has been notably decreasing with the increasing length of the road section to be reconstructed. Th erefore, it is recommended to reconstruct gravel roads in the longest possible sections.
Annual losses caused by the road accidents on improperly reconstructed gravel road sections are larger than onetime expenditures for taking of land for the planned right-of-way. Th erefore, it could be stated that the current practice in Lithuania to design the min possible deviation of the design road axis from the existing road axis is not reasonable from the technical and economic point of view.
Th e recommended corrections and supplements to the requirements of road design standards of the Republic of Lithuania are as follows: to replace the min radii of horizontal and vertical  curves with the radii values suggested in this work; to present the revised recommendations, suggest- ed in this work, for the compatibility of horizontal curve radii and the lengths of tangents between the curves; to supplement design standards with the con- cepts of 85 th -percentile speed (V 85 ), the Curvature Change Rate (CCR S ), traffi c safety criteria, traffi c safety modulus and its design levels; to change requirements for the determination of  V d -to specify that the value of V d shall be justifi ed by the calculations.