Driving Behaviour and Usability: Should In-Vehicle Speed Limit Warnings Be Paired with Overhead Gantry?

Round 1

Reviewer 1 Report

I have reviewed the manuscript, “Driving behaviour and usability: Should in-vehicle speed limit warnings be paired with overhead gantry?” and overall found this to be an interesting and most topical study (considering advancing connected vehicle technologies) presented within a well-written manuscript.

My comments are as follows:

Sample size computation and power calculation performed prior to recruitment (i.e.¸ was N = 20 intended sample or all that was able to be recruited in the time that allowed? Seems a relatively small sample even for a simulator study)?

It is noted that, “Participants were distributed into the two experimental conditions according to their age and gender” – how exactly did that occur? Were pre-checks done as to the demographic characteristics of drivers assigned to the different conditions?

Sixteen ANOVAs, eight ANOVAs etc – family-wise error rate – more conservative estimate of alpha applied?

It is noted that “Participants were told that the aim of the study was to gain more insight into an in-vehicle app conveying information on speed limits” – first, is it possible effects seen in this study were due to participants being more familiar with VSL on gantry’s than warnings delivered via HMI? And, it follows, that the current findings could also highlight that there is need to inform the public about the relative and potential combined roles of VSL and in-vehicle warnings? Also, were participants provided a debrief to outline the intended purpose of the study once their testing session had been complete (i.e., to compare across cells with warnings on HMI and VSL on gantries delivered at different time intervals)?

Were any checks conducted on whether trust in the speed information shown on the app influenced response to it?

A retrofitted device rather than in-built (the latter being the future to better integrate within the vehicle) would remove issues identified in first paragraph of the discussion associated with the mobile phone as HMI device used in the current study.

Author Response

Please see attachment.

Author Response File: Author Response.pdf

Reviewer 2 Report

This paper aimed to evaluate the effects of a mobile phone app that informed drivers of upcoming speed limits already conveyed via an overhead gantry on driving behaviour by the present driving simulator study. A novel result found in this study is that, although the VSL app was considered usable and accepted by the participants, they declared they would not be keen on such an app replacing the existing gantry and road signs. The following recommendations are made in relation to the content of this paper.

1、  In experimental design, it is stated that participants were distributed into the two experimental conditions according to their age and gender. For example, the younger a person is, the faster their reflexes are, so does age affect the results of the experiment. Please specify these.

2、  Please specify how participants are allocated in this article, whether they are allocated at random, or whether there is a specific allocation method.

3、  In the trig 500m experimental group, five repeated-measures ANOVAs were performed on page 9, line 257. Is there any literature to support the idea that five experiments are sufficient to illustrate the results?

4、  In discussion, a novel result found in this study is that, although the VSL app was considered usable and accepted by the participants, they declared they would not be keen on such an app replacing the existing gantry and road signs. What does this new discovery tell us about the real world?

5、  Please correct the format of this article to meet the requirements of the journal. Please see page 7, line 233.

Author Response

Please see attachment.

Author Response File: Author Response.pdf