Abstract
Travel time reliability (TTR) is widely used to evaluate transportation system performance. Adverse weather condition is an important factor for affecting TTR, which can cause traffic congestions and crashes. Considering the traffic characteristics under different traffic conditions, it is necessary to explore the impact of adverse weather on TTR under different conditions. This study conducted an empirical travel time analysis using traffic data and weather data collected on Yanan corridor in Shanghai. The travel time distributions were analysed under different roadway types, weather, and time of day. Four typical scenarios (i.e., peak hours and off-peak hours on elevated expressway, peak hours and off-peak hours on arterial road) were considered in the TTR analysis. Four measures were calculated to evaluate the impact of adverse weather on TTR. The results indicated that the lognormal distribution is preferred for describing the travel time data. Compared with off-peak hours, the impact of adverse weather is more significant for peak hours. The travel time variability, buffer time index, misery index, and frequency of congestion increased by an average of 29%, 19%, 22%, and 63%, respectively, under the adverse weather condition. The findings in this study are useful for transportation management agencies to design traffic control strategies when adverse weather occurs.
Highlights
Travel time reliability (TTR) is an important measure of traffic condition and is widely used to evaluate transportation system performance. e Federal Highway Administration (FHWA) [1] formally defined the TTR as “the consistency or dependability in travel times, as measured from day-to-day and/or across different times of the day.”e TTR can be used to represent the probability of on-time arrival; it is a key factor for roadway users to make decisions on travel routes and departure time
Yanan arterial road have obviously higher values than those of eastbound. e buffer time index (BTI) of these two routes are 0.56 (0.50) and 0.34 (0.32), respectively. e possible reason for this is that tidal traffic phenomenon on Yanan arterial road westbound can result in more frequent traffic congestions during afternoon peak hours
In order to investigate the impacts of adverse weather on TTR under different conditions, four scenarios are studied in this paper: (i) Scenario 1: the traffic on elevated expressway during off-peak hours (ii) Scenario 2: the traffic on elevated expressway during peak hours (iii) Scenario 3: the traffic on urban arterial road during off-peak hours (iv) Scenario 4: the traffic on urban arterial road during peak hours
Summary
Travel time reliability (TTR) is an important measure of traffic condition and is widely used to evaluate transportation system performance. E TTR can be used to represent the probability of on-time arrival; it is a key factor for roadway users to make decisions on travel routes and departure time. Lam [5] conducted a study in California and found that the value of travel time is $22.47 per hour (as 68 percentile of average salary at that time), while the value of TTR is $31.16 per hour (as 95 percentile of average salary at that time). There are several studies focusing on the relationship between TTR and traffic safety, and it is confirmed that the reduction of travel time reliability would lead to severe traffic collisions and crashes [6,7,8,9,10]. Some studies have found that improving travel time reliability can help reduce fuel consumption and emissions by avoiding stopand-go movements of vehicles [11, 12]. us, improving the TTR on the entire road network can be essential and valuable
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