Detail of JTG/T D21-2014

Introduction of JTG/T D21-2014

Codeofchina.com is in charge of this English translation. In case of any doubt about the English translation, the Chinese original shall be considered authoritative. According to the requirements of the Notice on issuing the 2009 Preparation and revision project plan of highway engineering standards (TINGGONGLUZI [2009] No.190) issued by the Ministry of Transport, China Highway Engineering Consulting Corporation is responsible for the preparation of the Guidelines for design of highway grade-separated intersections. Highway grade-separated intersection is an important specialty of highway survey and design. These guidelines are formulated with a view to improve the technical standard system of highway engineering, standardize the design of highway grade-separated intersections and meet the needs for development of highway construction in China. These guidelines are developed under the basic principles of "based on the domestic status quo, focus on key issues, reflection of the contemporary level and integration of modern concepts", taking operational safety as the main line, and showing the various considerations. Through absorbing the latest research results and design technologies of highway grade-separated intersections at home and abroad, a technical standard system of highway grade-separated intersections is established, ranging from control elements, overall design, scheme design, and geometric design to the design of renovated and expanded engineering. These guidelines consist of the following 14 clauses: 1 General provisions; 2 Terms; 3 Function and classification; 4. Control elements; 5 Overall design; 6 Interchange form; 7 Ramp cross-section; 8 Horizontal and vertical ramp alignment; 9 Ramp superelevation and widening; 10 Connection; 11 Ramp terminal at-grade intersection; 12 Access to other facilities; 13 Grade separation and overpass bridge; 14 Reconstruction and expansion of interchanges. In these guidelines, Clauses 1, 2, 3, 5 and 6 were drafted by Liu Zijian, Clause 4 by Zhou Ronggui, Clause 7 by Du Boying and Yu Yonghua, Clause 8 by Gao Hong, Clause 9 by Fang Jing, Clause 10 by Wang Bao, Clause 11 by Yang Shaowei, Clause 12 by Yang Shaowei and Shen Shunliu, Clause13 by Hu Sheng, and Clause 14 by Wang Xiaozhong. Guidelines for Design of Highway Grade-separated Intersections 1 General provisions 1.0.1 These guidelines are developed to standardize the design of highway grade-separated intersections. 1.0.2 These guidelines are applicable to the design of new construction, renovation and expansion projects of highways and highway grade-separated intersections and other facilities in needs of access. 1.0.3 Highway grade-separated intersections shall meet the requirements of function, safety and environmental protection, and the design shall take social conditions, traffic conditions, natural conditions, land use, full-life-cycle cost and other factors into comprehensive consideration. 1.0.4 Highway grade-separated intersections shall meet the traffic conversion function of nodes in the premise of ensuring the functions of highway network and cross highway. 1.0.5 The renovation and expansion design of highway grade-separated intersections shall be determined according to local conditions in combination with the current situation of existing projects and new traffic conditions. 1.0.6 In addition to these guidelines, the design of highway grade-separated intersections shall also comply with the current relevant standards of the nation and industry. 2 Terms 2.0.1 main line expressway in an intersection or Class I highway with arterial function, or highway that takes a dominant position in the interchange 2.0.2 minor cross highway other highway except the main line among the highways in an intersection 2.0.3 cross highway generic term for main line and minor cross highway 2.0.4 highway network node intersection of two or more highways in a highway network 2.0.5 access control control of traffic stream into and out of a main line 2.0.6 grade separation intersection between cross highways which are not interconnected 2.0.7 interchange intersection between cross highways which are interconnected 2.0.8 service interchange interchange that provides access and conversion functions for local traffic 2.0.9 system interchange interchange that provides continuous and rapid traffic conversion function between expressways, between expressway and Class I highway of arterial function or between Class I highways of arterial function 2.0.10 composite interchange combination of adjacent interchanges interconnected by auxiliary lanes, collector-distributor roads or ramps, etc. 2.0.11 interchange range segments of the main line and the minor cross highways affected by the geometric structure of interchange 2.0.12 net distance net distance between two facilities on the main line, including the distance from the end of the transition segment of acceleration lane to the start of the transition segment of next deceleration lane, from the end of the transition segment of acceleration lane to the tunnel entrance and from the tunnel exit to the start of the transition segment of deceleration lane 2.0.13 ramp road that connects cross highways in an interchange 2.0.14 exit ramp ramp for vehicles to leave the main line 2.0.15 entrance ramp ramp for vehicles to enter the main line 2.0.16 directional ramp ramp from which vehicles drive out and in directly in the turning direction (when turning right, vehicles drive out right and in right; when turning left, vehicles drive out left and in left) 2.0.17 semi-directional ramp ramp from which vehicles do not or not completely drive out and in directly according to the turning direction (when turning left, vehicles drive out left and in left; when turning right, vehicles drive out right and in right) 2.0.18 basic segment segment where vehicles run without being affected by divergence, convergence and weaving on the cross highway or ramp 2.0.19 basic number of lanes minimum number of lanes in the basic segment which is determined by the analysis of design traffic capacity 2.0.20 traffic stream line running route of one-way traffic stream 2.0.21 exiting-entering volume sum of the traffic volume exiting and entering the main line, i.e., the sum of the traffic volume of all exit ramps and entrance ramps   2.0.22 acceleration lane additional lane for vehicles to accelerate and enter the high-speed lane from the low-speed lane 2.0.23 deceleration lane additional lane for vehicles to decelerate and enter the low-speed lane from the high-speed lane 2.0.24 speed-change lane generic term for acceleration lane and deceleration lane 2.0.25 auxiliary lane additional lane for vehicles entering and leaving the main line to adjust the speed and distance, and change lanes, or additional lane parallel to the outside of the straight lane of main line for balancing lanes 2.0.26 collector-distributor road additional road arranged outside the main line and isolated from it to isolate the interweaving area and reduce the number of entrances and exits of the main line 2.0.27 gore nose circular end formed by the intersection of adjacent road surfaces at the diverging or converging connection 2.0.28 connection connecting part between ramp and cross highway, between main lines or between ramps, including connecting segment and gore nose of diverging and converging lanes, etc. 2.0.29 offset value required minimum width of the road surface between the outside of the diverging gore nose and the edge line of the adjacent lane 2.0.30 offset width value value of widening between the outer side of the diverging gore nose and the outer edge line of the hard shoulder to ensure the necessary offset value 2.0.31 lane balance keeping the number of lanes in each direction continuous or variable in the least range at the diverging and converging connections, so as to maintain the balance between the number of lanes before and after the divergence and convergence 2.0.32 ramp terminal at-grade intersection intersection between ramp and crossing highway or between ramps on the same plane 2.0.33 channelization way of guiding the vehicle's running track, reducing the conflict area or reducing the conflict points with traffic islands and marking lines at the intersection 3 Function and classification 3.1 General requirements 3.1.1 Highway grade-separated intersections shall provide continuous stream operation conditions for straight traffic of crossing highway by establishing spatial grade-separated intersection form. When the highway grade-separated intersections have the function of traffic conversion, the ramp shall be arranged to provide running conditions for the traffic conversion between the cross highways. 3.1.2 The adoption and type selection of highway grade-separated intersections shall be determined according to the position and function of nodes in the highway network system, and factors such as class, function and access control requirements of the crossing highways shall be comprehensively considered. 3.2 Classification 3.2.1 Highway grade-separated intersections can be classified into grade separation and interchange. 3.2.2 Interchange may be classified into two basic types, i.e., service interchange and system interchange, and may be classified according to the following requirements based on the number of intersection way, the shape of intersection, the way of intersection and the degree of directional connectivity, etc.: 1 Based on the number of intersection way, it may be classified into interchanges of three-leg intersection, four-leg intersection and multi-leg intersection. 2 Based on the shape of interchange, it may be classified into trumpet, cloverleaf, diamond, ring, turbine, T, Y and leaf interchanges. 3 Based on the intersection mode of traffic stream line, it may be classified into complete grade-separated intersection interchange and at-grade intersection interchange. 4 Based on the degree of directional connectivity, it may be classified into complete interchange and incomplete interchange. Explanation of provisions 1 When the number of intersection ways exceeds four, it is called multi-leg intersection. 3 In the complete grade-separated intersection interchange, all intersections between traffic stream lines are grade-separated intersection; in the at-grade intersection interchange, there is an at-grade intersection between some traffic stream lines. 4 In the complete interchange, all directions of traffic stream are connected. In the incomplete interchange, some directions of traffic stream are not connected, that is, lacking some traffic stream lines. The number of traffic stream line and the number of intersection way are in the following relation: N = n(n-1) (3-1) where, N——the number of traffic stream line; n——the number of intersection way. 3.3 Function and type selection 3.3.1 For highway network nodes at all classes, grade-separated intersection shall be selected according to the following requirements: 1 Expressway: Access shall be completely restricted, all nodes shall be grade-separated intersection, and the access distance and quantity of entrance and exit ramps shall be strictly controlled. Class I highway: Access shall be partially restricted. When it has the arterial function, the node intersecting with the Class I highway shall be grade-separated intersection; the node intersecting with Class II highway shall be grade-separated intersection; whether the node intersecting with highway below Class II is grade-separated intersection shall be determined according to access control requirements. When it has the function of collection and distribution, the node intersecting with the Class I highway with the function of collection and distribution should be grade-separated intersection; whether the node intersecting with highway below Class I is grade-separated intersection shall be determined according to requirements of access control and design traffic capacity. 3 Class II highway: according to the requirements of access control, design traffic capacity, site conditions and comprehensive benefits, individual nodes intersecting with highways of Class II and below may be grade-separated intersection. Explanation of provisions Access control puts forward the corresponding access methods, distance and quantity requirements for highways of different classes and functions, and serves as an important measure to ensure highway functions. Highway grade-separated intersection is an important means of access control, so highway class, function and access control and other requirements are important basis for adopting grade-separated intersection. 3.3.2 Service interchanges shall provide access and traffic conversion functions for local traffic. System interchanges shall meet the needs of continuous and fast passing through and traffic conversion. 3.3.3 The type selection of interchange shall meet the following requirements: 1 If the minor cross highway is a two-lane highway or a Class I highway with the function of collection and distribution, the interchange should be a service interchange. 2 If there is an intersection between expressways, expressways and Class I highways with arterial function, or Class I highways with arterial function, the interchange should be a system interchange. 3 Interchange with ramp toll stations may be designed according to service interchange. 4 The at-grade intersection may be used for the service interchange. 5 The complete grade-separated intersection should be used for the system interchange. 6 When there is no traffic conversion demand in individual directions, or there is a small amount of traffic conversion demand, but complete connectivity is particularly difficult, incomplete interchange may be used, and the traffic conversion function in unconnected directions shall be undertaken by adjacent nodes through highway network traffic organization, and shall be determined after comprehensive comparison and demonstration with complete interchange. Explanation of provisions 6 The research results and application practice at home and abroad show that it is very difficult to accurately predict the traffic volume due to the dynamic development of society, so there are great risks in meeting the use function for incomplete interchange, and if additional ramp is needed, its construction difficulty and input cost are greater than those built in one time. Therefore, whether to use incomplete interchange specified in this paragraph shall be determined after comprehensive comparison and demonstration. 3.3.4 When the nodes need traffic conversion, but grade separation is used due to distance control or site conditions, the turning traffic shall be undertaken by adjacent nodes through highway network traffic organization, and shall be determined after comparison with the interchange or the phased construction scheme of interchange and demonstration. 4 Control elements 4.1 General requirements 4.1.1 The control elements for design of highway grade-separated intersections shall include design vehicles, design speed, sight distance, traffic volume, service level and structure gauge, etc. 4.1.2 Control elements shall be taken as the basic basis for the design of highway grade-separated intersections. 4.2 Design vehicles 4.2.1 Passenger cars, large buses, articulated buses, heavy trucks and articulated trains are used as design vehicles in the design of highway grade-separated intersections, and passenger cars should be used as standard vehicles for traffic volume conversion. 4.2.2 When there are large transport needs of containers, major equipment, national defense, the largest vehicle should be used as the checking vehicle in the design of highway grade-separated intersections to check the design indicators such as the radius of circular curve, widening and sight distance of ramp and at-grade intersection turning lanes. When the traffic requirements of the largest vehicle are not met, the relevant technical indicators shall be adjusted. 4.3 Design speed 4.3.1 Within the range of highway grade-separated intersections, the design speed of crossing highway shall be the design speed of basic segment. When the crossing highway turns in the quadrant, the design speed within the interchange range may be appropriately reduced, but the difference between the design speed of cross highway and that of adjacent segment shall not be more than 20km/h. Explanation of provisions Crossing highway turning in quadrants includes crossing highway turning in the three-leg Y system interchange, and main traffic stream line turning in the four-leg system interchange quadrants. In order to ensure the continuity of the basic lanes, these traffic stream lines are designed according to the continuation segment of the cross highways, but their alignment indexes are often difficult to meet the standards of the basic segments, so this subclause specifies that their design speed may be appropriately reduced within the interchange range.

Contents of JTG/T D21-2014

Foreword ii 1 General provisions 2 Terms 3 Function and classification 3.1 General requirements 3.2 Classification 3.3 Function and type selection 4 Control elements 4.1 General requirements 4.2 Design vehicles 4.3 Design speed 4.4 Sight distance 4.5 Traffic volume and service level 4.6 Structure gauge 5 Overall design 5.1 General requirements 5.2 Basic data 5.3 Arrangement conditions 5.4 Distance control 5.5 Main line alignment conditions 5.6 Exit form 5.7 Lane continuity 5.8 Lane balance 6 Interchange form 6.1 General requirements 6.2 Key design points 6.3 Ramp form 6.4 Service interchange 6.5 System interchange 6.6 Interchange under special conditions 7 Ramp cross-section 7.1 General requirements 7.2 Composition and type of cross-section 7.3 Selection of cross-section type 8 Horizontal and vertical ramp alignment 8.1 General requirements 8.2 Horizontal ramp alignment 8.3 Ramp longitudinal profile 8.4 Exit ramp 8.5 Entrance ramp 8.6 Ramp toll plaza 9 Ramp superelevation and widening 9.1 General requirements 9.2 Cross slope and superelevation 9.3 Superelevation transition 9.4 Widening 10 Connection 10.1 General requirements 10.2 Speed-change lane 10.3 Mutual-diverging and mutual-converging main lines 10.4 Mutual-diverging and mutual-converging ramp 10.5 Continuous divergence and convergence 10.6 Auxiliary lane 10.7 Collector-distributor road 10.8 Weaving area 10.9 Gore nose structure 11 Ramp terminal at-grade intersection 11.1 General requirements 11.2 Sight distance 11.3 Straight road 11.4 Turning lanes 11.5 At-grade intersection at the minor cross highway side 11.6 Ramp at-grade intersection 12 Access to other facilities 12.1 General requirements 12.2 Service area 12.3 Bus stop 12.4 Parking area and viewing platforms 12.5 U-turn facilities 13 Grade separation and overpass bridge 13.1 General requirements 13.2 Scheme selection 13.3 Cross highway 13.4 Overpass bridge 14 Reconstruction and expansion of interchanges 14.1 General requirements 14.2 Basic data 14.3 Current situation evaluation 14.4 Reconstruction and expansion plan 14.5 Traffic organization Explanation of wording in these guidelines