Abstract: Because?the?empirical?design?approach?is?applied?to?the?former?design?of?U-turn?mouth,?there?are?always?some?inevitable?blemishes.?In?order?to?make?up?with?these?blemishes,?mathematical?knowledge?should?be?used?to?describe?the?U-turn?mouth.?Queuing?model?is?a?good?tool?to?modelize?the?U-turn?mouth?,which?theoretically?elaborates?the?nature?of?queuing?model?and?queuing?parameters.?Based?on?the?nature?of?queuing?model,?the?arrival?rate?and?dissipation?rate?are?the?cores?of?queuing?study.?In?U-turn?system,?probability?theory?is?mainly?used?to?deduce?theoretically.?On?the?theoretical?basis,?the?length?of?U-turn?mouth?can?be?determined?through?the?actual?traffic?survey,?and?whether?the?traffic?control?should?be?taken?for?U-turn?mouth?can?also?be?determined.

Key words: mathematical model , queue parameters , U-turn mouth , arrival rate , dissipation rate ;

摘要： 在以往的道路分隔带调头口的设计中,多是采用经验做法,这不免存在缺陷。为了弥补这一缺陷,必须对调 头口进行量化研究,用数学知识来描述调头口。排队模型就是个很好的工具,把调头口模型化,从理论上对调头口 的排队性质与排队参数进行论述。基于排队模型的性质,系统的到达率与服务率是进行排队研究的基础。在调头 口排队系统中,主要利用概率知识从理论上进行推导。在调头口排队理论基础上,通过实际交通调查即可确定调 头口的设计长度,也可决定调头口是否应该采取交通管制。

关键词: 数学模型, 排队参数, 调头口, 到达率, 服务率