ABSTRACT
Alignment consistency requirement at entrance and exit of highway tunnel, which is prescribed by design specification for highway alignment in China, limits the outcome of excellent design with safety and cost saving. Alignment consistency is redefined according to both safety and practicality for highway tunnel in this paper. Deviation distance from design trajectory to actual track, which cause by 3 seconds freezing steering wheel driving, is proposed to evaluate the consistency of horizontal alignment at tunnel entrance and exit. By quantitative analysis, spiral transition curve parameter A is found as a significant design index to guarantee the consistency. All alignment design condition can be included into three cases, which are analyzed respectively in detail. Regression formulas are deduced to guide highway designer to get a flexible and safe alignment of tunnel.
