5 th International Symposium on Highway Geometric Design. Country Report: Israel

Transcription

1 5 th International Symposium on Highway Geometric Design Vancouver, Canada, 2015 Country Report: Israel Shy Bassan 1 (corresponding author) Ran Zilbershtein 2 Benny Frischer 3 1 Dr. Shy Bassan, Amy Metom Engineers & Consultants, Ltd., 55A Yigal Alon St., Tel Aviv 67891, Israel. (Tel: ; fax: ) shy-b@amymetom-ta.co.il ; bassans@ netvision.net.il) 2 Ing. Ran Zilbershtein, Amy Metom Engineers & Consultants, Ltd. ran@amymetom.co.il 3 Dr. Benny Frischer, frischer@bezeqint.net Revised: April 27,

2 ABSTRACT: Highlights of the geometric design standards for rural (interurban) highways and urban freeways, published by Israel s Ministry of Transportation and the National Highways Company in 2012, are outlined. The preparation of these geometric design standards was accompanied and approved by a National Highways Company steering committee composed of highway design, highway safety, and traffic engineering experts from the MOT, the National Highways Company, the police traffic engineering department, and highway engineering consulting firms. The major objective of these design standards was to establish uniform rules and determine design values that would function as guidelines but not as mandatory regulations. The standards did not intend to limit the engineering view of thinking, but they do provide a desirable frame in which to present design options and enable the highway engineer to cope with non-conventional situations during the design process. The paper first documents the objectives, structure, and major sections of the standards. A specific section introduces Israel data and statistics of population, roadway length, motorization, kilometers traveled, and traffic accidents (with casualties) information. The second part gives an overview of recent developments in design policy, highway cross section, stopping sight distance, and horizontal alignment. Finally, it presents topics for discussion related to sight-distance restrictions in horizontal curve design and left-shoulder principles on divided highways. 2

3 INTRODUCTION The design of interurban transportation infrastructure is important for the economy and for the fast growth rate of car ownership. The main requisites that highway-design guidelines should maintain are the following: mobility and accessibility needs, safety of road users, efficient traffic operations, landscape harmonization, and minimum environmental deterioration. The major objective of highway geometric design standards is to establish uniform rules and determine design values that function as guidelines but not as mandatory regulations. The standards do not intend to limit the engineering view of thinking, but do provide a desirable frame in which present design options and enable the highway engineer to cope with non-conventional situations during the design process. The 2012 Israeli highway design guidelines are based on a literature overview of recent international guidelines (AASHTO 2004, 2011; TAC ATC 1999, 2009; New Zealand TRANSIT 2003; Austroads 2009; DMRB 1999; and German guidelines RAA 2008). The main innovations of these guidelines relate to the topics of design speed and level of service policy; sight distance and equivalent deceleration (or equivalent friction) criteria, which directly affect the outcome of vertical and horizontal alignment; divided highway cross section, which is related to recent developments in safety-barrier concepts and technologies; and a new model for correlating horizontal radii and superelevation. The structure concept of the guidelines is that they should be easily implemented by the users. Each section includes a brief background, definitions of terms and basic issues, major considerations and assumptions in determining the recommended design values, warrants if needed, recommendations of design values, and tables, illustrations, relevant drawings, and schematic sketches for clarifications. The design process requires the integration of guidelines from the different topics into one pack in order to propose an appropriate design solution for a specific project. The guidelines principally refer to new highway projects but also to upgrading existing roadways. Exceptional design values that are due to unusual situations and constraints (e.g., topography, right of way [ROW], environmental issues) are possible if given approval by the design authorities after considering a specific problem. The guidelines usually present minimum or maximum desirable and/or absolute values. The highway engineer should 3

4 strive not to follow directly these design values in an extreme manner but to implement a balanced design that incorporates suitable values after considering the topography, environment, and construction cost, on the one hand, and highway safety and traffic operations, on the other hand. The guidelines structure enables periodic updating according to practical experience, safety impacts, and the design policy of Israel s Ministry of Transportation. The guidelines volume depicted in this report is Volume I: Geometric Design of Interurban Highways: Road Sections. Additional volumes include Volume II: Intersections; Volume III: Interchanges and Junctions; and Volume IV: Compact Grade Junctions. Volume III and Volume IV will be updated as one unified volume and are still in practice. This ongoing work is accompanied by the same steering committee previously described. An additional volume refers to Road Tunnels and has a specific and expanded geometric design chapter. It was first published in November 2012 by the Ministry of Transportation and the National Highways Company. Its authors represent several disciplines (in addition to highway design and traffic engineering), such as construction, structural engineering, geo-mechanics, ventilation, fire safety, electric lighting and communication systems, and environment. ISRAEL TRANSPORTATION AND TRAFFIC STATISTICS Population and roadway length: Israeli population for the second quarter of the year 2015 is approximately 8.32 million. This estimation does not include foreign workers. The total roadway length in Israel roadway network estimated for 2013 is: 18,825 kilometers from which 6608 kilometers are interurban roadways, 10,586 kilometers are urban roads and 1,631 kilometers are access roads. Motor vehicles and kilometers traveled: The number of motor vehicles estimated for 2014 is 2,966,000, from which 2,457,000 are private vehicles, 328,000 trucks, 124,000 motorcycles, 20,000 taxis, 32,000 buses (and minibuses), and 4600 special service vehicles. The total million kilometers travel (MKT) estimated for the year 2013 includes 51,207 [10 6 veh km per year] from which: 37,848 private cars, 9099 trucks, 1666 buses (and 4

5 minibuses), 1640 taxis, 872 motorcycles. 31,157 (out of 51,207) is the annual MKT for interurban roadways estimated for The average kilometers traveled per vehicle is: 18,100 km/vehicle. This number is the equivalent average for several vehicle types: km/private cars, km/trucks, km/minibus, km/bus, km/taxi, and 7200 km/motorcycle. The rate of motorization estimated for the year 2014 is 358 vehicles per 1000 inhabitants, from which 292 vehicles per 1000 inhabitants (82%) are private cars. Road accidents with casualties The number of road accidents with casualties estimated for the year 2013 is 13,048 (9720 in urban roads and 3328 in interurban roadways). This number includes: 252 fatal accidents (from which 86 accidents with pedestrian involved and 119 collisions with moving vehicles), 1413 serious accidents, and 11,383 slight accidents. The distribution of road accidents by accident type is presented in Table 1: Table 1: Annual distribution of road accidents with casualties by accident type, accident severity and road type; Israel 2013 Accident type and severity Total Fatal Serious Slight Collision with moving vehicle Collision with parked (or stopped) vehicle Collision with a fixed object Hitting a pedestrian Injury to passenger on vehicle Overturning Running of road skidding other Total (year 2013) Urban roads 9, Interurban roadways 3,

6 The relevant number of casualties estimated for the year 2013 is 24,294 from which 277 killed, 1624 seriously injured, and 22,393 slightly injured (out of 24294) casualties occurred in urban roads and 8720 (out of 24294) casualties occurred on interurban roadways. 131 (out of 277) people were killed in urban roads accidents and 146 (out of 277) people were killed in interurban roads accidents. The annual accident rate per population [accidents per inhabitants] is 162. The annual accident rate per kilometers traveled [accidents per 10 6 veh km per year] is Both rates are calculated for the year The annual accident rate per kilometers traveled [accidents per 106 veh km per year] for interurban roadways is Appendix A presents several charts plotting the country statistics information over the years and comparing the results between Israel and several countries (Greece, Italy, France, UK, Germany, Canada, U.S.A.). The country statistics traffic and transportation data presented, is based on Israel Central Bureau of Statistics (CBS) database. VOLUME I: LIST OF CONTENTS Section 1: Introduction Section 2: Basic Design Policy Highway categories and hierarchy and the basic characteristics of each category; determination of target speed, design speed, and implementation criteria; design definitions for divided-highway final construction phase after its initial stage of construction as a twolane highway (one-way roadway). Section 3: Highway Cross Section The highway cross-section components according to highway categories; pavement width, including lane, shoulder and median widths; side slopes; forgiving road design and infrastructure; intermediate specific cross sections (1+1, including separation devices, passing lanes, and climbing lanes). Section 4: Sight Distance Typical sight distance categories for the design of the highway alignment: stopping sight distance, decision sight distance, passing sight distance, and constrained passing sight distance. 6

7 Section 5: Horizontal Alignment Design criteria and details of the design components of the horizontal alignment: horizontal radii, superelevation, widening, superelevation transition (superelevation runoff, tangent runout), spiral curves, hairpin curves, design controls, and sight-distance relevance. Section 6: Vertical Alignment Design criteria and details of the design components of the vertical alignment: longitudinal grades and critical length, vertical curve design, grade impact on heavy vehicle performance (deceleration, acceleration), design control, initial recommendations for escape ramps. Section 7: Combinations of Horizontal and Vertical Alignment Rules for combinations of the design components covered in previous sections for a complete spatial and aesthetic design; qualitative and visual description of a desirable and an undesirable design. Section 8: Highway Capacity and Level of Service (LOS) Definitions of terms (e.g., flow rate, traffic volume, traffic density, PHF, FFS, PTSF). Criteria and methodology for computing traffic-flow measures for determining the highway s LOS (freeway, urban freeway, multilane divided highway, two-lane undivided highway), capacity estimation, typical LOS design measures, and other traffic characteristics. The section refers to HCM 2000 guidelines. Section 9: Integration of Bicycle Traffic on the Interurban Highway Network Basic design values, arrangements and warrants for bicycle paths or bicycle lanes in the highway cross section, typical geometric design components for bicycle traffic. Section 10: Integration of Public Transport on Interurban Highways Overview of public transport solutions (bus lane, bus way), integration of public transport traffic in the cross section, treatment of bus stops and their geometric design elements on interurban highways. Section 11: Urban Freeways Definitions and characteristics, typical design values, geometric design characteristics for highway sections and interchanges, and urban aspects. 7

8 Section 12: Integration of Rest Areas on Interurban Highways Rest area categories, geometric design specifications, warrants, spacing between rest areas, parking space determination, distance from intersections. Section 13: Access to Infrastructure Facilities on Interurban Highways Implementation policy, geometric design specifications for access from existing intersection and road sections, distance from intersection. DEVELOPMENTS AND HIGHLIGHTS Basic Design Policy and Cross Section Elements Design speed and target speed The target speed is the desirable travel speed in the defined highway category. The goal is for most vehicles in the traffic stream to be able to travel at such a speed during free-flow conditions. It is desirable that the maximum speed limit be similar and actually identical to the target speed. The design speed is the safest speed that is determined for the highway geometric design and its geometric components, which influence vehicle operation. Israeli policy indicates that in order to provide a reasonable safety margin (similarly to other civil engineering disciplines and in accordance to international guidelines and literature overview), the value of the design speed is in practice 10 km/hour faster than the value of the target speed on the interurban network. Highway classification and functional characteristics Interurban highways are classified as follows in the Israeli guidelines: Freeway: The freeway is supposed to transfer high traffic volumes at high speed conditions or, preferably, free-flow speed (FFS). The road is characterized by optimal mobility and no direct access to any adjacent land use. A freeway has at least two separated roadways with two lanes or more for each direction of travel. The connection between the freeway and other highways is made only by system interchanges. The recommended design speed range for a freeway is km/hour. A freeway sign has a blue rectangular perimeter and the freeway number has usually one blue digit. 8

9 Urban freeway: The urban freeway has almost the same geometric characteristics as a freeway. These urban highways generally cross metropolitan regions, and therefore their interchange/junction density is higher than that of freeways. The minor road of these interchanges could be an urban arterial, so that the traffic pattern and daily distribution are different from those on freeway interchanges in non-urban regions; i.e., there is a higher level of traffic congestion. The recommended design speed range for urban freeways is km/hour. An urban freeway sign has a blue rectangular perimeter and its number has usually two or three blue digits. Major highway: Major highways transfer high traffic volumes between different regions of the interurban network at considerably high vehicle speeds. They have a high mobility level for long trips and limited access to adjacent land use. These highways are usually divided into two separated roadways, one for each direction of travel; but in certain occasions, they can be designed as two-lane highways for the first stage of construction. The main difference between major highways and freeways is the possibility of the major highways connecting to crossing highways at signalized intersections. The divided major highways' design speed range is km/hr or km/hour if they include signalized intersections. The twolane major highways' (with intersections only) design speed range is km/hr. A major highway sign has a red rectangular perimeter and its number has usually two red digits. Minor (regional) highway: The regional highway serves moderate trip lengths and functions as a feeder roadway to the major highways. The regional highway has a certain level of mobility but serves enclosed land uses, as well. Regional highways can be designed as divided highways or two-lane 9

10 highways. The divided minor highway design speed range is identical to that of major highways. A regional highway sign has a green rectangular perimeter and its number has usually three green digits. Local and access roads (low-volume roads): The principal role of local roads is the provision of access to enclosed land uses. They serve short-length trips and are usually designed as two-lane, undivided roads. Their design speed range is km/hour. Low-volume roads are categorized as local roads but could have some reductions in certain design criteria. The sign of local or access road has a black rectangular perimeter and its number has usually four black digits. Table 2 summarizes design policies and major cross-section design characteristics of highways by categories. 10

11 Table 2: Highway design speed, LOS, and cross-section summary of Israeli interurban highway design guidelines Highway category Subject Freeway Urban freeway Major highway Minor (regional) highway Design speed (km/hour) Divided: (1) Two lane: Divided: (1) Two lane: Level of service C (level terrain) D (other) D D D (level or rolling terrain) E (mountainous terrain) Number of ways (road) 2 (at least) 2 (at least) 2 (usually) 1 (occasionally) 1 (usually) 2 (occasionally) Lane width (m) 3.6 or 3.7 (120 km/hour) (80 km/hr) 3.5 (70 km/hr) 3.3 (60 km/hr) Right shoulder width (m) (80 km/hour) 2.0/2.5 (60/70 km/hr) 1.2 (2 lanes per Left shoulder width direction) (m): divided highway 3.0 (3 or more lanes only per direction) 1.2 (2 or 3 lanes per direction) 3.0 (4 or more lanes per direction) 1.2 (2 lanes per direction) 3.0 (3 or more lanes per direction) 1.2 (2 lanes per direction) 3.0 (3 or more lanes per direction (1) For highways with interchanges: km/hour. For highways with intersections: km/hour. (2) Lane width of 3.0 m for low-volume roads. Local (access) road E (60-80 km/hr) (2)

12 Stopping sight distance and sight-distance design policy A major purpose in highway geometric design is to ensure that the driver is able to see any possible road hazard in sufficient time to take action and avoid an accident. Stopping sight distance (SSD) is the most important of the sight-distance considerations since sufficient SSD is required at any point along the roadway. SSD is the distance that the driver must be able to see ahead along the roadway while traveling at or near the design speed and to safely stop before reaching an object whether stationary or not. SSD can be limited by both vertical and horizontal curves. The fact that it impacts the design radius of both curves makes SSD so fundamental in the geometric design process. The stopping sight distance has two components: (1) the distance traveled during the driver s reaction time; (2) the distance traveled during braking. This distance can be determined by the following formula: where: SSD Minimum stopping sight distance (m) V d d t R tr Vd SSD= Vd + (1) d Design speed (km/hr) Deceleration of passenger cars (m/s 2 ), equivalent to the longitudinal = friction coefficient (f) multiplied by the acceleration of gravity (g) Perception reaction time (s), usually 2.5 seconds The formula assumes level terrain. Ascending grade decreases the SSD, and descending grade increases the SSD. The recommended equivalent deceleration rate (d) is based on an SSD model developed by Lamm et al. (1999) and by research conducted in the U.S. (Fambro et al. 1997, AASHTO 2011). This weighted deceleration takes into account modern braking systems; the quality of tires, which strongly affects the skidding longitudinal friction coefficient between a wet pavement and the tires; and the quality of the pavement (e.g. SMA asphalt concrete). The equivalent friction coefficient and weighted deceleration are presented in Table 3. The stopping sight distance (SSD) values are presented in Table 3, based on the weighted deceleration recommended values and Equation

13 Table 4: Equivalent Deceleration, Friction, and SSD Values Recommended for Design Speed Recommended values Design speed (km/hr) f eq : Israel d (m/s 2 ) : Israel f eq : recommended d (m/s 2 ) : recommended (Israel 2012) SSD (m) Israel 2012 Design SSD (m), rounded for design (Israel 2012) Table 3 presents the recommended SSD values and the design values for different countries: Australia (Austroads 2003, 2009), New Zealand (Transit 2003), Canada (TAC 1999), U.S.A. (AASHTO 2011), Germany (RAS 1995), Lamm et al. 1999, and Ireland (NRA 2007). 13

14 Table 4: Minimum Stopping Sight Distance Design Values (m) for Several Countries Country t R (sec) Design Speed (km/hr) Israel (2012) Australia (2003) New Zealand (2002) Ireland (2007) Canada (1999) USA (2011) Germany (1995) Lamm et al. (1999) Israel (1994) t R Perception-reaction time (seconds). A graphical relationship between the recommended SSD values and the design speed values according to the geometric design guidelines of different countries (Table 3) is presented in Figure 1. The Canadian SSD design values are identical to Israel (1994) SSD design values for the design speed range of km/hour. Therefore, their lines are unified in the chart and we can see the Canadian purple line only. The Israeli recommended SSD values (Israel 2012) are smaller than the Israel (1994) values due to the higher (and improved) equivalent deceleration rates as presented in Table 3. 14

15 Fig. 1: Comparison of Minimum Stopping Sight Distance in Several Countries and Recommended Values Level Terrain The Israeli recommended SSD values are around the average at the design speed range of km/hr. As the design speed rises, the SSD values approach the lower values (Australia 2003, 2009; Lamm et al. 1999). The recommended sight distance design (SD) values for decision sight distance, passing sight distances (PSD), and constrained passing sight distance (CPSD) are presented in Table 5. The constrained passing sight distance (CPSD) is the threshold sight distance below which overtaking is prohibited for all vehicle types. It means that the even fast vehicles should prevent making passing maneuver under these circumstances. Any two lane highways' segment which does not satisfy the CPSD should be marked with double solid continuous line in its centerline. Such signing (in Israel highways and typically internationally) informs the driver that a passing maneuver is prohibited. Most passenger car drivers practically need a distance shorter than the conventional (and somehow conservative) passing sight 15

16 distance (PSD). For example the passing maneuver becomes shorter than PSD when the vehicle being passed is a slow vehicle and its traffic speed is much lower than the speed limit; therefore the passing maneuver can be conducted with almost no delay and the driver of the passing vehicle does not have to accelerate. Such example emphasizes a possible implementation of the CPSD. Further detail of the elements of passing sight distance (d1, d2, d3, d4) can be found in NCHRP 605 (2008). Figure 2 introduces these passing maneuver elements in two lane highways. The Israeli constrained passing sight distance (CPSD) implementation assumes lower values of these elements. d1, d2, d3, d4 interpretation: d1: perception and reaction; d2: passing maneuver; d3: safety margin; d4: distance traveled by the oncoming vehicle Fig. 2: Elements of passing sight distance (based on NCHRP 605, 2008). 16

17 Table 5: Decision SD, passing SD, and Constrained Passing SD Design Values (Israel) Sight distance (m) Design Speed (km/hr) Decision SD Passing SD * * Constrained passing SD * * * Speeds applicable only to divided highways in Israel Implementation of sight distance design values: The sight distance (SD) design values are implemented on the basis of highway category as presented in Table 6. Table 6: Implementation of SD Design Criteria Highway Category Sight Distance (SD)Type Freeway / Urban freeway 2-Way Divided: Major highway / Minor highway 2-Lane Undivided: Major highway 2-Lane Undivided Minor (regional) highway Local (access) road Stopping SD Always Always Always Always Decision SD Basic for design * Prior to interchange or intersection (lane reduction or increase) Passing SD (km) Constrained Passing SD (CPSD) Prior to interchange or intersection (lane reduction or increase) Each 0.05 Vd(km/hr) For SD < CPSD: passing prohibited (100%) by appropriate marking lane reduction or increase Each 0.05 Vd(km/hr) For SD < CPSD: passing prohibited (100%) by appropriate marking Enable CPSD every 3 km at least. * On freeways and long trips on highly trafficked highways with considerably high operating/target speeds, without traffic flow interference (such as intersections and access to proximate land uses), the design policy requires drivers SD to be longer than Stopping SD (i.e. Decision SD) in order to make the driving calm and comfortable. 17

18 Table 7: Object Height and Driver Eye Height on SD Edges Sight Distance (SD) Type Driver Eye Height (m) [passenger car] Object Height (m) Stopping SD 1.05 Decision SD 1.05 Undivided highway: 0.15 Two-way (divided) highway: 0.60 * Prior to intersection or interchange: * (road sections generally higher-speed highways) Passing SD and Constrained Passing SD 1.05 * Concepts based on AASHTO 2011, Fambro et al. (NCHRP 400) * ("the portion of the vehicle height that needs to be visible for another driver to recognize a vehicle") If the highway is designed as a divided two-way highway, only one way is opened for traffic in the first stage (i.e. a two-lane highway), then implementation of the SD policy (specifically for the design of vertical curves) would be based on two-lane highway design requisites. Horizontal curve design A proper design of highway horizontal curves should strive for the maximum curvature or the minimum radius just under the most critical conditions. It is therefore necessary to establish an appropriate relationship among the design speed, the horizontal curve radius, and the superelevation. The minimum radius or the maximum curvature has a limiting value for a given design speed as determined according to the maximum rate of superelevation (e max ) and the maximum side-friction coefficient (f Rmax ): R min = V (g e 2 d max + g f R max V = ) 127 (e where: R min minimum radius of horizontal curve (m) V d design speed (km/hr) g e max = a e superelevation acceleration g f Rmax = a fr friction lateral acceleration a c = a e +a fr centrifugal acceleration 127 conversion factor, taking acceleration of gravity as g=9.81 m/s 2 2 d max + f R max ) (2) 18

19 The use of a smaller radius (sharper curvature) than the minimum radius for the prevailing design speed might necessitate a non-practical superelevation or side-friction coefficient beyond the safety limits. Table 8 presents the design values of the basic parameters in horizontal curve design. Table 8: Design Values of Basic Parameters in Horizontal Curve Design Parameter e max (max superelevation) Design Speed (km/hr) f Rmax max side friction ** f Rmin min side friction * R min min horizontal radius (m) γ: e-f R distribution coefficient * Adapted from Lamm et al. (1999). ** f Rmax is required for the minimum horizontal curve radius calculation. Relationship between Radii Larger than Rmin and the Appropriate Superelevation: e-r Model The distribution of the amount of side friction (f R ) and superelevation (e) is very important in the design of horizontal curves with radii larger than the minimum. If a radius selected for the horizontal curve is larger than the minimum radius (R min ), then the horizontal curve should be designed to a smaller superelevation than the maximum superelevation (e max ). The superelevation and the side friction assist in balancing the centrifugal force while driving along a horizontal curve. The ratio (e/(e+f)) depicts the relative contribution to balancing the centrifugal force: as this ratio increases, the circular motion relies less on the side friction, the centrifugal deceleration decreases, and driving becomes more comfortable and safe along the horizontal curve. The e-r model assumes a linear relationship between f R and e, and two pairs (f Rmax, e max ; f Rmin, e min ) characterize this relationship. If we define γ as the e-f R linear distribution 19

20 coefficient based on the superelevation design policy (Bassan 2013), the final of formulation of the "e-r" model is as follows: where: R V d e(r) 2 = 1 Vd e (R) frmax + e γ, e 1+γ 127 R max min e e max (3) prevailing radius of the horizontal curve (m) design speed (km/hr) prevailing superelevation for R>Rmin f Rmax maximum side-friction coefficient for maximum superelevation (Table 8) e max maximum superelevation suitable for a specific design speed (Table 8) γ = e-f R distribution coefficient, based on maximum superelevation policy (Table 8). This coefficient depends on f Rmax, f Rmin, e max, e min. Fig. 3: Linear e-f R distribution model results, e max = 0.10 for 60 Vd 80 km/hr, and e max = 0.08 for 90 Vd 120 km/hr 20

21 TOPICS FOR DISCUSSION Sight-distance restriction in horizontal curve design Barriers along open highways and walls on tunnels may restrict the available sight distance in the design of horizontal curves. The minimum radius that is based on the equilibrium of the centrifugal force, Rmin = V 2 /(e max +f Rmax ), is too small for the requirements of stopping sight distance when there are obstructions along the road (especially the median barrier on open roadways) that intrude on the line of sight. The limitation of a stopping sight distance could arise as follows: (1) On two-lane highways, the inside barrier could restrict sight distance in the rightbound curve. The horizontal sight-line offset (HSO) could be no more than 4.8 meters (3 meters of right shoulder plus 1.8 meters of the distance between the centerline of the right lane and its right edge). (2) On four (or six)-lane divided highways, the median barrier could restrict sight distance in the left-bound curve. The HSO could be no more than 4.8 meters (3 meters of median/left shoulder width plus 1.8 meters of the distance between the centerline of the left lane and its left edge). The HSO could be even smaller (i.e. 3.0 meters) if the median shoulder is reduced to 1.2 meters. The outside barrier restriction is similar to two-lane highways (HSO=4.8 m); however, since design speed is usually higher, the stopping sight distance is even more restricted. All this is even more obvious in tunnels, where continuous walls run along the sides. Table 9 present examples of SSD restrictions on a horizontal curve, based on AASHTO (2011). Figures 4 and 5 show the restricted SSD line (AB) for two-lane highways and sixlane divided highways, assuming HSO = 4.8 m and Rmin = 229 m, Rmin = 501 m (for V d = 80 km/hr, and V d = 110 km/hr) correspondingly. 21

22 Table 9: Examples of SSD restrictions on horizontal curves, based on AASHTO SSD design values SSD restrictions Design speed, V d (km/hr) Stopping sight distance, SSD (m), AASHTO Calculated radius (HSO=4.8m) * Calculated radius (HSO=3.0m) * Minimum radius (Rmin), e(max)=8%, AASHTO 2011 * R = SD 2 / (8 HSO) Fig. 4: Example of a Restricted SSD Line for a Two-Lane Highway (V d =80 km/hr) 22

23 Fig. 5: Example of a Restricted SSD Line for a Six-lane Divided Highway (V d =110 km/hr) Median (left) shoulder width The current Israeli design policy recommends a median shoulder width of 1.2 meters for divided interurban highways with two lanes per direction and of 3.0 meters for divided interurban highways with three or more lanes per direction. The concept is that 3.0 meters enables a stalled vehicle in the left-most lane to move aside to the median shoulder instead of conflicting at least two traffic lanes while trying to make a safe maneuver to the right shoulder. On the other hand, a second opinion supports a narrow left shoulder that is suitable for highway capacity and high target-speed requirements. The assumption is that drivers are used to moving to the right shoulder when they have to stop for emergency reasons (i.e. stalled vehicle or strong personal difficulty in continuing to drive, etc.). This opinion, however, supports widening the right shoulder (to more than 3.0 meters) and possibly considering wide emergency lay-bys (generally implemented in working zones) on the right-hand side in order to provide a wider space for the driver to open the vehicle door and not be put at risk from the ongoing traffic on the left hand side. Still, a narrow left shoulder results in smaller HSO and, therefore, in more restricted sight distances on horizontal curves as discussed earlier. 23

24 REFERENCES (1) American Association of State Highway and Transportation Officials (AASHTO) (2011). A Policy on Geometric Design of Highways and Streets, 6 th Edition. Washington D.C. (2) Bassan S. (2013). Modeling the relationship between the radius and superelevation in horizontal curve design. Proceedings of the Transportation Research Board 92 nd Annual Meeting, Washington DC, January. (3) Design Manual for Roads and Bridges (DMRB) (1999), Vol. 2: Highway Structures Design, Section 2: Special Structures, Part 9: Design of Road Tunnels, BD 78/99, HMSO, U.K. (4) Fambro B., Fitzpatrick K., Koppa R.J. (1997). Determination of Stopping Sight Distance. National Cooperative Highway Research Program (NCHRP), Report 400, Transportation Research Board, Washington D.C. (5) Transportation Association of Canada (1999). Geometric Design Guide for Canadian Roads. (6) Guidelines for the Design of Roads (RAS). (1995). Part: Alignment (RAS-L), Proposals, 1993 and German Road and Transportation Research Association, Cologne, Germany. (7) Guidelines for the Design of Motorways (2011 [2008]). Road and Transportation Research Association. FGSV. RAA. Germany (8) Guide to Road Design, Part 3: Geometric Design (2009). AGRD03/09, Austroads, Sydney, New South Wales. (9) Harwood D.W., Fambro D.B., Fishburn B., Herman J., Lamm R., Psarianos B. (1995). International sight distance practices. Proceedings of International Symposium on Highway/ Geometric Design Practices, pp (10) ISRAEL Central Bureau of Statistics (CBS). Transport and communications. 24

25 (11) Lamm R., Psarianos B, Mailaender T. (1999). Highway Design and Traffic Safety Engineering Handbook. McGraw-Hill, New York. (12) National Roads Authority, Design Manual for Roads and Bridges (2007). Volume 6: Road Link Design. Ireland. (13) NCHRP 605 (2008). Passing Sight Distance Criteria. National Cooperative Highway Research Program. Transportation Research Board. Washington D.C. USA. (14) Austroads (2003). Rural Road Design. A Guide to the Geometric Design of Rural Roads. (15) TRANSIT New Zealand (2003). State Highway Geometric Design Manual. 25

26 APPENDIX A: ISRAEL TRANSPORTATION AND TRAFFIC STATISTICS INFORMATION: GRAPHICAL PRESENTATION Roadway length: 26

27 Motor vehicles and kilometers traveled: 27

28 Rate of motorization: 28

29 Rate of motorization (continued): 29

30 Road accidents with casualties 30

31 Road accidents with casualties (continued) 31