Results
The researcher has gathered data using the radar gun survey method. The data were grouped into two categories according to the weather conditions relevant for the study: the traffic during the dry weather (and, by extension, the dry road surface) and the wet weather. The data from a total of 827 cars were analysed, with 435 for during dry weather conditions and 392 during wet weather (Table 4-9).
The data was analysed to determine the relationship between the average speed on the road and the weather conditions and, therefore, to establish if the high accident rate can be tied to the changing conditions of driving. The results have shown that the average speed of the vehicles observed during the dry weather is 31 mph, with a standard deviation of 4.3 mph (Table 4-2).
When applied to the cumulative frequency polygon, the results have turned out to be consistent with the established speed limit: the current limit on the Albion Way being 40 mph, while the percentile curve results have shown the 34 mph as the 85th percentile of distribution (figure 4-8). The analysis of the wet weather conditions has yielded very similar results.
The average speed of vehicles was identical with the insignificantly bigger standard deviation (Table 4-6). Accordingly, the cumulative frequency polygon has produced an identical result of 34 mph as the 85th percentile (figure 4-12). Both analyses were supported by the chi-square analysis (Morrison & Henkel 2009), which has shown that the data in both cases had followed the normal distribution (accepted at 1% level of confidence).
The comparative analysis of the spot speeds confirms the uniformity of the speeds, with a statistically insignificant increase in the wet weather (Table 4-9). Finally, the comparison of the headways among the vehicles has indicated no significant difference between the dry and wet weather (figure 4-15).
Three conclusions can be drawn from the results. First, the traffic on the Albion Way is consistent with the regulations of official speed limits. Of the 827 cars observed, only two have exceeded the 40 mph limit (Table 4-5), with the average speed being well within the acceptable range. The researcher thus concludes that reckless driving can be safely excluded from the list of potential causes of the high accident rate, at least based on the sole criterion of the speed limit violation. Second, the drivers show little to no concern regarding the weather conditions.
The difficult driving conditions associated with the wet road have long been established as one of the primary causes of the traffic accidents (Brijs, Karlis, & Wets 2008), and while technically there is no separate speed limit for the wet weather, the drivers are regularly advised to exercise caution while driving under such circumstances (Driving in adverse weather conditions 2016). The comparison of the descriptive statistics, as well as the data on headway duration, clearly shows no consideration of the increasingly hazardous environment.
The latter is especially crucial as the data was gathered on the bend, which presents additional dangers during the slippery conditions. What is more, both of the speed limit violations mentioned above occurred during the wet weather, as did the higher frequency of the vehicles passing the bend at the higher speed (Table 4-10).
Thus, the following situation is observable: while no formal traffic rules are being violated on the regular basis, the drivers do not consider weather as a reason to raise caution and do not alter their driving style to decrease the possibility of an accident. In other words, if we assume that the picture is the same most of the time (which is confirmed by the chi-square tests, presented in tables 4-3 and 4-7), it appears like the speed limits of the Albion Way are unacceptable at least for the wet conditions.
Limitations
The research has several limitations. First, there is no reliable statistical data available on the accident rates that could be applied to the data on the observed speed. Thus, the conclusion regarding the connection between the lack of caution displayed during the periods of wet weather and the increased number of accidents is preliminary and requires further inquiry.
The same can be said about the tendency displayed in comparing the average headway during different weather conditions: while the shorter headway presents the higher probability of the accident when the road is slippery, there is no direct evidence of the correlation between the two sets of data. Thus, while such a conclusion is consistent with the findings of the previous studies (Andreescu & Frost 1998; Yau 2004), the available data does not allow to confirm it with certainty. Second, the conclusion regarding the consistency of the speed limit with the safety requirements dictated by the Albion Way may equally apply to the dry conditions, as the data presented in this research does not allow to assess the degree to which the difficulty of passing the bend (or driving on the road) rises with the change of the weather.
Third, the research specifically targets the sole factor responsible for the increased risk of the accident, while other possible factors, such as the lighting conditions, are left outside the scope. As lighting can be equally important (Golob & Recker 2003), additional research is needed to analyse it and possibly compare its degree of influence to that of the slippery road surface. Fourth, the data did not account for the seasonal factor. While the study gives an equalized picture, the actual setting may vary as the intensity and frequency of precipitation varies according to the seasonal change (Erdogan et al. 2008).
Recommendations
Despite the preliminary nature of the study, the following recommendations may be outlined. First, while the intuitive assumption is that the citizens of Manchester are used to driving in the wet conditions and are aware of the additional risks it creates and the preventive measures that need to be exercised (Bergel-Hayat et al. 2013), the analysis suggests the need for additional training or at the very least minor public information events that would raise the awareness of the importance of such measures, both on the Albion Way and, presumably, in the other areas.
Second, while there is no conclusive proof that the accident rate will decrease with the change of the speed limit, the analysis does show the possibility of such outcome, so additional research is required to complete the picture by providing the data on other factors that affect the phenomenon, such as the lighting and the design of certain sections of the road.
Third, once such data is obtained, the method used by the researcher can be applied to analyse other areas of Manchester where evidence exists of the hazardous driving conditions. If the assumption regarding the poor understanding of the risks associated with the wet weather is correct, such analysis will help to localise the issue and apply timely measures if necessary.
Reference List
Andreescu, M P & Frost, D B 1998, ‘Weather and traffic accidents in Montreal, Canada’, Climate Research, vol. 9, no. 3, pp. 225-230.
Bergel-Hayat, R, Debbarh, M, Antoniou, C, & Yannis, G 2013, ‘Explaining the road accident risk: Weather effects’, Accident Analysis & Prevention, vol. 60, pp. 456-465.
Brijs, T, Karlis, D, & Wets, G 2008, ‘Studying the effect of weather conditions on daily crash counts using a discrete time-series model’, Accident Analysis & Prevention, vol. 40, no. 3, pp. 1180-1190.
Driving in adverse weather conditions 2016.
Erdogan, S, Yilmaz, I, Baybura, T, & Gullu, M 2008, ‘Geographical information systems aided traffic accident analysis system case study: city of Afyonkarahisar’, Accident Analysis & Prevention, vol. 40, no. 1, pp. 174-181.
Golob, T F & Recker, W W 2003, ‘Relationships among urban freeway accidents, traffic flow, weather, and lighting conditions’, Journal of Transportation Engineering, vol. 129, no. 4, pp. 342-353.
Morrison D & Henkel R 2009, The significance test controversy, Transaction Publishers, New Brunswick.
Yau, K 2004, ‘Risk factors affecting the severity of single vehicle traffic accidents in Hong Kong’, Accident Analysis & Prevention, vol. 36, no. 3, pp. 333-340.