XI International Symposium "ROAD ACCIDENTS PREVENTION 2012"

Novi Sad, 11st and 12nd October 2012.

UDK:

PROJEKTI SANACIJA OPASNIH MJESTA NA CESTAMA U REPUBLICI HRVATSKOJ

„BLACK SPOT“ RECONSTRUCTION PROJECTS ON THE

ROADS IN THE REPUBLIC OF CROATIA

Josip Bošnjak1, Ivan Molnar2

Sažetak U Republici Hrvatskoj je identificirano 339 opasnih mjesta od čega je u zadnjih deset godina izvršena sanacija 261-og opasnog mjesta što se bitno odrazilo na sigurnost cestovnog prometa. Uspjeh sanacije opasnog mjesta ovisi o utvrđivanju uzroka i okolnosti prometnih nesreća i primijenjenoj metodologiji sanacije. Najveći broj prometnih nesreća događa se zbog superpozicije više faktora od kojih su najznačajniji nepovoljni horizontalni i vertikalni odnosno prostorni elementi ceste u kombinaciji s pogreškama vozača, vremenskim uvjetima, odvodnjom ceste, okolišem i neusklađenom prometnom signalizacijom. U radu su prikazani primjeri primijenjenih projektnih rješenja sanacije opasnih mjesta na državnim i županijskim cestama primjenom novih tehnologija projektiranja cesta i 3D vizualizacije koja omogućuje sinergiju građevinskog i prometnog rješenja u svim fazama izrade projekta sanacije opasnog mjesta. Ključne riječi: projekti cesta, opasna mjesta, vizualizacija Abstract: In the Republic of Croatia there has been 339 „black spots“ identified from which 261 were reconstructed in the last ten years thus increasing traffic safety. The success of the black spot reconstruction depends on determining the cause and the circumstances of the traffic accidents and the applied methodology of the reconstruction. The largest number of traffic accidents occurs due to superposition of multiple factors form which the most relevant are unfavorable horizontal and vertical or spatial elements of the road in combination with drivers errors, weather conditions, road drainage and environment that is uncoordinated with traffic signalization. The paper presents examples of applied project solutions for „black spots“ reconstructions on state and county roads by applying new technologies of road design and 3D visualization that enables synergy between engineering and traffic solutions in all of the phases of reconstruction project. Key words: road design projects, „black spots“, visualization ________________________________________________________________________________________________ 1 mr. sc. Josip Bošnjak, dipl. ing. građ, Rencon d.o.o. Vijenac I. Mažuranića 8, Osijek, RH, josip.bosnjak@rencon.hr 2 Ivan Molnar, dipl. ing. prom, Rencon d.o.o. Vijenac I. Mažuranića 8, Osijek, RH, ivan.molnar@rencon.hr

‐ 2 ‐ 

 

1. INTRODUCTION

Through many years of experience in road design, Rencon Ltd. made several road design projects of „black spot“ reconstruction on state and county road in Republic of Croatia. Those projects proved to be exquisite for presentation and experience exchange, thus reducing number of accidents and increasing traffic safety. In table 1. statistical data are shown regarding consequences of traffic accidents on 27 „black spots“ on state and county roads in Republic of Croatia. Presented data are collected in the last 4 years before design projects were made and works executed. First nine „black spots“ (marked in blue) were on crossroads, next three (marked in red) were in larger crossroad area, and the rest were on sections outside the settlements.

Table 1. Statistical data regarding traffic accidents before „black spot“ reconstruction

During design phase, grouping of traffic accidents was observed depending on „black spot“ location – on the crossroad or on the section outside the crossroad. On nine „black spots“ on the crossroad, one of the main reason for accidents was location of the crossroad (just after the convex curve) or insufficient visibility caused by fences, vegetation or advertising boards. Typical example of „black spot“ on the crossroad described in this paper is „Bašarinka“. On three „black spots“ located in crossroad proximity (250m radius) one of the main reason for accidents, beside low visibility was combination of pure horizontal and vertical road elements or disregarding of the norms and design rules. Typical example of „black spot“ of such kind described in this paper is „Žminj“.

‐ 3 ‐ 

 

On the next fifteen „black spots“ located on open sections of state or county roads, one of the main reason for accidents is: pure horizontal and vertical road elements (pure spatial road position – bad combination of horizontal and vertical curves), irregular engineering elements (without transition curves, without widening in the bend, without superelevation or with inadequate superelevation appropriate to design speed or radius) in combination with pure pavement condition (cracks or slippery pavement) or non compliance with the norms or design rules. Typical example of „black spot“ of such kind described in this paper is „Oblakovac“.

Figure 1. Map of Croatia with locations of 27 „black spots“

2. GENERAL ABOUT „BLACK SPOTS“

Traffic infrastructure is rarely considered as the cause for traffic accidents. Traffic accidents are not evenly distributed over

overall road network. Locations of increased risk on which accidents occur more often are known as „black spots“. Unfortunately the entire database for traffic accidents is available only to few people exclusively inside the police and it is

used for planning preventive or repressive actions. Apparent database with all traffic accidents and their micro locations (available to all services for road management) could contribute to faster insight of potentially dangerous places in earliest phase, as input for road reconstruction projects or as feedback after the reconstruction is executed. If some section is not recorded as „black spot“ (due to insufficient number of accidents) designers don´t have information about this location to which they should pay special attention while making new projects. In the same way they don´t have feedback about accidents on reconstructed sections in order to help them from making new „black spots“ by implementing standard solutions or even not standard solutions. In making revisions of the projects, positive experience form „black spots“ reconstruction must be applied.

Evaluation of success in „black spot“ recovery is proportional to the quality of determination the cause of traffic accidents, and is consider as vital part of the process to increase traffic safety.

To the officials that manage the roads the traffic infrastructure is basic tool for improving safety and especially in order to

reduce the weight of the aftermath of traffic accidence. Investment in road infrastructure is the biggest and most demanding part of the prevention. According to 2008/96EC directive on road infrastructure safety from 19th of November 2008. Traffic safety on existing roads should be increased by revision of project documentation and by targeted investments in improvement of sections with the largest number of traffic accidents and/or highest potential for accidents reduce.

Traffic accidents are not wholly random event. One accomplice to traffic accidents is often set of circumstances that contributed in making insurmountable obstacles for the driver. Dangerous sections outside the settlements are most often in the part of the road with adverse and irregular elements, respectively incompatible with rules and norms for road design. Drivers study potential hazard based on their experience and perception and solved then in specific sequence. Even the most experienced drivers have trouble assessing pure horizontal and vertical road elements (irregular superelevetion, low friction,

‐ 4 ‐ 

 

size of the bend after vertical saddle ...). If they don´t know horizontal and vertical visibility respectively if they are driving by hart and don´t adjust their speed there is a great chance for traffic accident.

It is very difficult to inform drivers about all circumstances in different atmospheric conditions by traffic signs. Only possibility for greater impact on traffic accidents are construction projects that will eliminate all the „unknowns“.

In order to increase traffic safety it is necessary to start with the reconstruction as soon as possible after project are finished. Reconstruction of existing crossroad into roundabouts is often applied as one solution for „black spot“ recovery. The main

advantage of a roundabout in comparisons with standard crossroad is controlled reduction in approaching speed resulting in minor consequences. Temporary (mountable) roundabouts can be applied, which are efficient and economically payable. Mountable roundabout is immediately applicable in existing space, but such solution is only temporary until final solution or reconstruction is applied. Main advantage, apart instant functionality, is low initial cost and no long term procedure for solving property or legal relations and permits. It is even possible to spot some disadvantages in the design and correct them it in final stage. As a temporary solution – experimental (mountable) roundabouts are possible in order to explore different size and shape before final decision.

When thinking of mountable roundabout first impression is New Jersey, but there are more elegant solutions that can be applied in tourist areas without big impact on the environment.

Central island can be marked with flowerpots and approaching islands can be marked with gray flexible poles with reflective (class III) foil and Swarovski crystals at the top and bottom. Beside esthetic appearance such mountable roundabout is easily set and removed. Flexible poles serve as visual barrier, they are reflective and in case of impact they don´t cause and damage on the vehicles.

One example of such elements and equipment for mountable roundabout is shown in figure 2.

Figure 2. Visualization of mountable roundabout

3. EXAMPLES OF RECOVERY OF THREE „BLACK SPOTS“ IN CORATIA From 27 „black spots“ three locations are specified on state and county roads as examples. Black spot „Bašarinka“ is

located in the crossroad, „Žminj“ is in crossroad proximity and „Oblakovac“ is on the open section of the road. According to processed statistical data for all 27 „black spots“ form 688 traffic accidents 68% (469) happened during dry

weather and pavement, 79% (548) during good visibility in daytime, and average age of the participants was 37.35 years.

‐ 5 ‐ 

 

Table 2. Traffic accidents throughout the year

 

Table 3. Traffic accidents throughout the week

 

4. EXAMPLE 1 BLACK SPOT „BAŠARINKA“ – crossroad CR5002 and CR2039 (section: Poreč – Novigrad)

Figure 3. „Black spot“ "Bašarinka" (Rencon Ltd.)

39

52

45

48

55

47

90

60

54

51

54

93

35

45

55

65

75

85

95

siječanj veljača ožujak travanj svibanj lipanj srpanj kolovoz rujan listopad studeni prosinac

mjesec

br.

pro

m. n

esr

eća

102

98

110

89

99

111

79

75

85

95

105

115

ponedjeljak utorak srijeda četvrtak petak subota nedjelja

dani

br.

pro

m.

nes

reća

‐ 6 ‐ 

 

„Black spot“ is four-spoke crossroad with two county roads CR5002 and CR2039, outside the settlement. Traffic signalization is insuficient with many advertising billboards next to the road. Those billboards distract drivers because they intertwine with traffic signs and thus reducing concentration. Public lighting is present at the crossroad.

Figure 4. Existing traffic signalization

According to police reports, there are several causes for traffic accidents: unadjusted speed (31%), disregarding right of

way (26%), wild game (17%). Alcohol was present in 22% of the drivers that were involved in traffic accidents. Most accidents occurred during the day (70%) in dry pavement condition (74%).

Further analysis showed additional information about accidents on this frequent crossroad, especially during summer months with high speeds on main route. Main reasons, beside driver´s error are related to traffic intensity, environment and reduced visibility due to vegetation and billboards.

Recovery proposal for this „black spot“ is to convert it to roundabout, given that there are problems with property or legal relations it was decided to make two phases: firs one will be a mountable roundabout and the second will be permanent roundabout. Mountable roundabout will be with radius Rv=14m. In second phase, final roundabout will be with radius Rv=40m.

Figure 5. New traffic signalization

‐ 7 ‐ 

 

5. EXAMPLE 2 BLACK SPOT „ŽMINJ“ – section CR5077 (section: Pazin - Pula)

Figure 6. „Black spot“ "Žminj" (Rencon Ltd.)

„Black spot“ is the section of county roads CR5077 outside the settlement with low visibility bend and irregular crossroad

in „X“ shape. Pavement is 8,0m wide made without cross fall, smooth but with cracks. Traffic signalization is incomplete and there is no public lighting.

Figure 7. Existing traffic signalization

According to police reports, only cause for traffic accidents is unadjusted speed (100%). Alcohol was present in 22% of the

drivers that were involved in traffic accidents. Most accidents occurred during the day in dry pavement condition. Further analysis showed additional information about accidents on this bend with crossroad in the proximity. Bend with low visibility and irregular horizontal and vertical elements are to blame for almost all traffic accidents. On

„Žminj“ location general layout of the road is specific as well as the lack of horizontal visibility (vegetation, wall). Given that and with the combination with the „X“ shaped crossroad is the cause for traffic accidents.

Traffic accidents occurred in the manner that the vehicle proceed straight in the bend and go of the road due to high speed or moves to opposite lane and collide with incoming vehicle. Existing traffic signalization is incomplete due to frequent accidents.

Recovery proposal for this „black spot“ is possible only by reconstruction of spatial elements of the route, cross section and different shape of the crossroad accordant to norms and design standards.

‐ 8 ‐ 

 

Based on the analysis of the existing state and traffic accidents the recovery of the “black spot” was designed in the way that: Intersection with the local road is placed outside the bend of the road, Horizontal elements of the road are adjusted to the design speed and the road category (the transverse slope of the

pavement is being fixed and the widening of the road is being done), Two-sided protective fence is being placed between two pavements for visual guidance and as a physical barrier, Visibility is enhanced by removing the vegetation on the side of the road, Appropriate horizontal and vertical traffic signaling and equipment is placed, Solar LED markers are placed.

Figure 8. The situation of newly designed traffic signaling

With the recovery of the “black spot” horizontal elements of the bend of the road are being corrected and the increase of

speed through the bend is achieved. Although there were no traffic accidents that happened during the night, by removing the vegetation from the direction of Pula, it is possible that the lighting coming from the settlement (150m from the bend of the road) will create a false impression with the drivers and suggest the wrong direction of the route towards the settlement. To visually underline road route and prevent the wrong impression of the bend solar LED markers are placed on the side of the road as well as the road axis – the dividing line of the road.

Figure 9. Road bend marked with LED solar markers

Rencon ltd. has used these markers in a number of “black spot” recovery projects. The analyses of the statistical data

regarding accidents and possible solutions in some cases showed the necessity of emphasizing spatial experience of the road in

‐ 9 ‐ 

 

the conditions of poor visibility. Poor spatial relations between different traffic elements (side roads, railway etc.) caused bad judgments by drivers and numerous accidents. When putting up public lighting or doing major modifications to road route is not an option the solution is in emphasizing traffic lanes and sides of the road.

Solar markers can be best used in approach lanes to intersections located outside of settlements. The character of the road (higher driving speeds) and limited options for classic lighting methods (large distances to existing power grids) represent a danger and higher possibility of seeing the intersection too late. 6. EXAMPLE 3 “BLACK SPOT OBLAKOVAC” – ROAD SECTION D51 (road section: Požega – Nova Gradiška)

 Figure 10. “Black spot Oblakovac" (Rencon ltd.)

“Black spot” is a part of the state road, a road bend in a notch outside a settlement. Pavement is made of two traffic lanes, with a total width of 6.0m. Asphalt is smooth and traffic signaling incomplete. There is not lighting of the road.

According to police reports the cause of accidents is only high speeds. All traffic accidents occurred during the day in conditions of wet pavement coming from Nova Gradiška towards Požega (longitudinal slope of -4%).

Figure 11. The situation of existing traffic signaling

The causes for traffic accidents were determined by detailed analyses of traffic accidents and drawing the collision point

diagrams – irregular pavement warping, inadequate horizontal and vertical visibility, poor spatial road route guidance, state of the pavement, inadequate technical elements of the road regarding speed limitations, inadequate pavement width in the bend. Road bend elements are satisfactory for speeds up to 70 km/h, and speed limit is set at 90 km/h.

‐ 10 ‐ 

 

Figure 12. The situation of newly designed traffic signaling

Based on the analysis of the existing state and traffic accidents recovery of “black spot” was designed accordingly:

Speed limitation based on technical elements of the road – from 90km/h to 70km/h, Vertical radius is set to max 4%, Road routes horizontal elements are adapted to design speed and road category (transverse pavement slope and

widening of the bend is being made), Appropriate horizontal and vertical traffic signaling and equipment is placed, Horizontal visibility is increased.

Since this is a “black spot” recovery for additional horizontal and vertical visibility check a 3D visualization of the road and

surrounding environment was made.

Figure 13. Visualization of “black spot” Oblakovac

Analyses of horizontal and vertical visibility have a significant role in road designing when it comes to safe and

comfortable driving experience since 95% of all environment information is received through our eyes. Field of vision has to be in-sync with road elements and the quantity of information must not be overloaded with too many traffic signs, billboards and tourist signalization.

‐ 11 ‐ 

 

Figure 14. Visualization of “black spot” Oblakovac

Irregular overtaking and stopping visibility can be a cause for traffic accidents with severe consequences. It is not enough to use a classic 2D analysis to determine the right visibility distance but we need to use 3D visualization of the road and surrounding environment. To use all the advantages of computer technology in 3D road design it is vital to keep pace with the fast development of computer hardware and software. As a tool to check horizontal and vertical visibility the standard AutoCad Civil 3D package, which in its 2012 version has an option for visibility check as well as Drive option for drive simulation, can be used.

7. CONCLUSION

Roads are seldom declared as a main cause of traffic accidents, unlike drivers or vehicles. In three examples we have shown in this article, about “black spots” in state or county roads, most often the main reasons for traffic accidents are poor horizontal and vertical road elements, road route that is adapted to the terrain, temporary solutions due to unsolved property rights or urgency of the procedure, financially more acceptable solutions, mistakes in designing and/or improperly performed reconstructions.

Huge potential and most effective way of increasing road traffic safety lies in road infrastructure. Existing road sections can only be improved by reconstruction, correcting irregular and unfavorable horizontal and vertical elements and synchronizing them with current Laws, regulations and norms in road design. Using the positive experiences in “black spot” recovery as we have shown in our examples by combining construction and traffic solutions and use of 3D visualization software can be of great help in designing roads. 8. LITERATURE

[1] Directive 2008/96/EC of European parliament and Council, November 19th 2008. [2] Rule book on basic conditions that public roads outside of settlements must comply to regarding road traffic safety (NN 110/01) [3] Lj. Roso, D. Tušar, D. Šegavić: Recovery of “black spots” as one of the measures of increasing road traffic safety on state roads,

Professional Counseling Road traffic safety on Croatian roads, proceedings, Pula November 26th and 27th 2009. [4] J. Bošnjak, I. Molnar: Recovery of “black spots” as a function of road traffic safety, Opasni mesta (crni točki) na patištata vo Republika

Makedonija, Skopje June 21st 2010. [5] Conceptual and implementation design for “black spot” recovery on state and county roads in Croatia; "Rencon" ltd. Osijek 2008-2011.