In this paper, we derive the value of a signal obtained by a traveller prior to the choice of departure time. The signal does not have to be a perfect prediction of the travel time. It is sufficient that it carries information about the travel time. The traveller may then consider the distribution of travel time conditional on the signal to increase her expected utility by making a better informed choice of departure time.

We show that a signal always increases the expected utility compared to the situation without any signal. For a broad class of signals, the expected utility is monotone with respect to signal strength. Furthermore, we demonstrate that even perfect travel time information does not necessarily eliminate the cost of travel time variability and we establish necessary and sufficient conditions for when it does. We find that the predictable part of travel time variability may or may not be costly, depending on the shape of the traveller's scheduling utility at the origin of the trip. Using estimates of scheduling preferences from the literature, we show that the cost of predictable travel time variability may constitute a substantial part of the total cost of travel time variability. In a particular case of scheduling preferences, travel time distribution and noise distribution, we establish an analytic relationship between the strength of the signal and the expected utility of the trip and evaluate the marginal cost of signal weakness. This knowledge may facilitate design and cost-benefit analysis of traveller information systems and policies decreasing travel time variability.

在本文中，我们推导了旅行者在选择出发时间之前获得的信号值。该信号不必是行进时间的完美预测。携带有关旅行时间的信息就足够了。然后，旅行者可以根据信号做出旅行时间的分配，以通过更好地知情选择出发时间来增加其预期效用。

我们表明，与没有任何信号的情况相比，信号总是会增加预期效用。对于广泛的信号类别，预期的效用在信号强度方面是单调的。此外，我们证明，即使是完美的旅行时间信息也不一定能消除旅行时间可变性的成本，并且我们会为其建立必要且充分的条件。我们发现，旅行时间可变性的可预测部分可能会或可能不会很昂贵，这取决于旅行者在行程起点的调度工具的形状。使用来自文献的调度偏好的估计，我们表明可预测的出行时间可变性的成本可能构成出行时间可变性总成本的重要部分。在安排偏好设置的特定情况下，行程时间分布和噪声分布，我们建立了信号强度与行程预期效用之间的解析关系，并评估了信号弱化的边际成本。这些知识可能有助于减少旅行者时间可变性的旅行者信息系统和策略的设计和成本效益分析。