Service Level Study Of Urbanized First-Class Highway With Access Points

With the emergence of urbanized highways,the number and types of access points on highways’ sides have gradually increased.However,since existing road networks in China have not yet considered access roads into the technical grade system,corresponding design specifications and technical standards of access roads are lack.Access points often have great impacts on highway traffic operations.Due to the large number of lanes and fast design speed,impacts of access points on first-class highways are more prominent.Therefore,this thesis carries out the study on service levels analysis of urbanized first-class highways with access points,and proposes optimal design and management strategies of access points.First of all,based on characteristics of urbanized first-class highways and considering geometric forms,the types of access points along the urbanized first-class highways are divided into four categories,A,B,C,and D,of which: A and D accesses are right-in and right-out,which have the least impact on the traffic operation of highway segments and have higher safety.However,the D-type access adopts the form of a harbor and the land area is large.In the geometric form statistics of 80 accesses along a segment of G107 in Zhengzhou City,Type A accesses account for 67%.Therefore,Class A accesses are the key research object.The access land use determines the vehicle composition of the generated traffic.Using the unmanned aerial vehicle(UAV)to collect data on the access,the impact process of vehicle entering and exiting at the access on the traffic operation of the first-class highway segment is analyzed.Conclusions show that:(1)The passenger car mainly occupies the outermost lane when entering and exiting.The time to enter and exit is short and the impact range is small.(2)Trucks of different sizes need to occupy 2 or even 3-4 lanes outside,which has a large impact range.(3)There is a significant feature of occupying the space-time resources of the lanes on the highway segment.Secondly,considering the passenger car as the standard model,based on the driving time,this thesis proposes a method for estimating the conversion coefficient of vehicles on highway segments.Taking into account characteristics of space-time resources of lanes on highway segments,a method for estimating the conversion coefficient of vehicles at the access is proposed.An example analysis is carried out on a G107 segment with a land use type of logistics park in Zhengzhou City.The rationality and applicability of proposed vehicle conversion coefficient calculation models are verified.The relationship between speed and other traffic flow parameters are explored.Conclusions are: in the steady flow state between the free flow and the saturated flow,there are many vehicles,and the distance is between the free flow and the saturated flow.The vehicle at the access is more convenient when entering or exiting the highway segment.However,it often affects multiple vehicles on highway segments,and the vehicle conversion factor is relatively large at this time.Furthermore,based on the highway service level analysis method in the Highway Capacity Manual(2016 edition),the vehicle conversion coefficient is introduced into the traffic density calculation process of the highway segment including accesses,and the corresponding service level can be obtained according to the density threshold range.Combined with the example application and comparative analysis of a segment of G107 in Zhengzhou under the presence and absence of accesses,conclusions are drawn as follows:(1)The impact of the access on the reduction of the service level of highway segments cannot be ignored.(2)When the service level is at A or B levels,the difference in density between the two conditions is small.As the density increases,the service level decreases,and the difference in density begins to increase gradually.When the density is higher,the service level drops to E or F.The density difference is also large.Finally,layout and design principles and signal control strategies of access points on first-class highways are discussed.VISSIM simulation results show that the control strategy is effective only when the traffic volume of the highway segment upstream the access is close to the capacity,and on this condition.At this time,the traffic flow that can actually pass downstream increases by 6%-9%..