This study investigates drivers＇ diversion decision behavior under expressway variable message signs that provide travel time of both an expressway route and a local street route. Both a conventional cross-sectional ...This study investigates drivers＇ diversion decision behavior under expressway variable message signs that provide travel time of both an expressway route and a local street route. Both a conventional cross-sectional logit model and a mixed logit model are developed to model drivers＇ response to travel time information. It is based on the data collected from a stated preference survey in Shanghai, China. The mixed logit model captures the heterogeneity in the value of ＂travel time＂ and ＂number of traffic lights＂ and accounts for correlations among repeated choices of the same respondent. Results show that travel time saving and driving experience serve as positive factors, while the number of traffic lights on the arterial road, expressway use frequency, being a middle-aged driver, and being a driver of an employer-provided car serve as negative factors in diversion. The mixed logit model obviously outperforms the cross-sectional model in dealing with repeated choices and capturing heterogeneity regarding the goodness-of-fit criterion. The significance of standard deviations of random coefficients for travel time and number of traffic lights evidences the existence of hetero- geneity in the driver population. The findings of this study have implications for future efforts in driver behaviormodeling and advanced traveler information system assessment.展开更多
Background:There is a substantial interest in the values that consumers place on drinking water quality and supply.Financial resources are crucial to improving the urban potable water supply in developing countries th...Background:There is a substantial interest in the values that consumers place on drinking water quality and supply.Financial resources are crucial to improving the urban potable water supply in developing countries that are characterized by low-cost recovery rates and a high and rapidly growing demand for more reliable services.This study examined households’willingness to pay(WTP)for the improvement of water services by identifying their water choice decisions and the mode of water supply that they prefer the water supply authority to use among several alternative water supply options.Stated-preference data were collected from 322 randomly selected households in Addis Ababa,who were presented with three sets of choices(three alternative bundle choices,including the reference scenario).The data were analyzed using the mixed logit WTP space model.Three approaches to modeling the distribution of WTP(fixed,uncorrelated,and correlated)using mixed logit WTP space models were compared.Results:Three-quarters of the households agreed to contribute money toward ecosystem-based water supply management(EBWSM)intervention programs on a monthly basis.The average contribution that the respondents were willing to pay was 150.5 Ethiopian Birr(ETB)as a one-off lump sum to kick off the EBWSM activities.Most of the respondents chose a bundle of water supply options that provides risk-free and high-quality water with no months of shortages than moderate water quality that is safe to drink and palatable with 1 month shortages annually.This implies that households would need to be supplied with risk-free,high-quality water without interruption at an appropriate flow pressure.The model with correlations fitted the data well with the highest simulated log-likelihoods at convergence and gave the best estimate of the households’WTP for water improvement.Nearly 46%of the sampled households were willing to pay more than 33 ETB per month,and 49%of the households were willing to pay between 21 ETB and 33 ETB per month for the monthly water bill.Overall,approximately 95%of the sampled households were willing to pay more than 21 ETB.Conclusion:Customers are willing to pay to avoid most types of water supply restrictions.Moreover,WTP is sensitive to the scope of service improvement,income,affixed price,and elicitation method.In summary,mixed logit WTP-space models can help accurately predict household-level WTP,which can be used to select improvements in drinking water access and services in the Legedadie-Dire catchments.展开更多
Understanding the temporal stability in the factors influencing drivers' injury severity in single-vehicle collisions would help evaluating the effectiveness of implementing different safety treatments so that res...Understanding the temporal stability in the factors influencing drivers' injury severity in single-vehicle collisions would help evaluating the effectiveness of implementing different safety treatments so that researchers could understand whether any safety improvements,observed after applying a certain safety treatment, are attributed to the specific treatment or simply attributed to the temporal instability of the factors being addressed. This study investigates the temporal stability of the factors affecting drivers' injury severity in singlevehicle collisions involving light-duty vehicles. The study is based on utilizing ordinal regression modeling to analyze the severity of drivers' injuries in all police-reported lightduty single-vehicle collisions that occurred in North Carolina from January 1, 2007, to December 31, 2013. A separate regression model was estimated for each year so that statistical significance of each risk factor may be compared over the years. The study also estimated random-parameter(mixed) ordered logit models to explore the heterogeneity in data. The most significant factor that was found to increase the severity of drivers' injuries in light-duty single-vehicle collisions is driving under the influence of alcohol or illicit drugs. Other significant factors, in decreasing order in terms of their significance, include driving on a highway curve, exceeding speed limit, lighting conditions, the age of the driver, and the age of the vehicle. In contrast, there were six factors that were found to be significant in only some years and not in all years. These six temporally unstable factors include the use of seatbelt, driver's gender, rural highways, undivided highways, the type of the light-duty vehicle, and weather and road surface conditions. These same factors were found by other previous research studies to be significant and stable predictors of drivers' injury severity in single-vehicle collisions.展开更多
基金supported by a project (No. 51008195) funded by National Natural Science Foundation of Chinaa Shanghai First-Class Academic Discipline Project (No. S1201YLXK) funded by Shanghai Government+1 种基金a project (No. 14XSZ02) funded by University of Shanghai for Science and Technologya project funded by Key Laboratory of Road and Traffic Engineering of the Ministry of Education, Tongji University
文摘This study investigates drivers＇ diversion decision behavior under expressway variable message signs that provide travel time of both an expressway route and a local street route. Both a conventional cross-sectional logit model and a mixed logit model are developed to model drivers＇ response to travel time information. It is based on the data collected from a stated preference survey in Shanghai, China. The mixed logit model captures the heterogeneity in the value of ＂travel time＂ and ＂number of traffic lights＂ and accounts for correlations among repeated choices of the same respondent. Results show that travel time saving and driving experience serve as positive factors, while the number of traffic lights on the arterial road, expressway use frequency, being a middle-aged driver, and being a driver of an employer-provided car serve as negative factors in diversion. The mixed logit model obviously outperforms the cross-sectional model in dealing with repeated choices and capturing heterogeneity regarding the goodness-of-fit criterion. The significance of standard deviations of random coefficients for travel time and number of traffic lights evidences the existence of hetero- geneity in the driver population. The findings of this study have implications for future efforts in driver behaviormodeling and advanced traveler information system assessment.
文摘Background:There is a substantial interest in the values that consumers place on drinking water quality and supply.Financial resources are crucial to improving the urban potable water supply in developing countries that are characterized by low-cost recovery rates and a high and rapidly growing demand for more reliable services.This study examined households’willingness to pay(WTP)for the improvement of water services by identifying their water choice decisions and the mode of water supply that they prefer the water supply authority to use among several alternative water supply options.Stated-preference data were collected from 322 randomly selected households in Addis Ababa,who were presented with three sets of choices(three alternative bundle choices,including the reference scenario).The data were analyzed using the mixed logit WTP space model.Three approaches to modeling the distribution of WTP(fixed,uncorrelated,and correlated)using mixed logit WTP space models were compared.Results:Three-quarters of the households agreed to contribute money toward ecosystem-based water supply management(EBWSM)intervention programs on a monthly basis.The average contribution that the respondents were willing to pay was 150.5 Ethiopian Birr(ETB)as a one-off lump sum to kick off the EBWSM activities.Most of the respondents chose a bundle of water supply options that provides risk-free and high-quality water with no months of shortages than moderate water quality that is safe to drink and palatable with 1 month shortages annually.This implies that households would need to be supplied with risk-free,high-quality water without interruption at an appropriate flow pressure.The model with correlations fitted the data well with the highest simulated log-likelihoods at convergence and gave the best estimate of the households’WTP for water improvement.Nearly 46%of the sampled households were willing to pay more than 33 ETB per month,and 49%of the households were willing to pay between 21 ETB and 33 ETB per month for the monthly water bill.Overall,approximately 95%of the sampled households were willing to pay more than 21 ETB.Conclusion:Customers are willing to pay to avoid most types of water supply restrictions.Moreover,WTP is sensitive to the scope of service improvement,income,affixed price,and elicitation method.In summary,mixed logit WTP-space models can help accurately predict household-level WTP,which can be used to select improvements in drinking water access and services in the Legedadie-Dire catchments.
基金financially supported by a Science and Engineering Research Grant provided by the Emirates Foundation
文摘Understanding the temporal stability in the factors influencing drivers' injury severity in single-vehicle collisions would help evaluating the effectiveness of implementing different safety treatments so that researchers could understand whether any safety improvements,observed after applying a certain safety treatment, are attributed to the specific treatment or simply attributed to the temporal instability of the factors being addressed. This study investigates the temporal stability of the factors affecting drivers' injury severity in singlevehicle collisions involving light-duty vehicles. The study is based on utilizing ordinal regression modeling to analyze the severity of drivers' injuries in all police-reported lightduty single-vehicle collisions that occurred in North Carolina from January 1, 2007, to December 31, 2013. A separate regression model was estimated for each year so that statistical significance of each risk factor may be compared over the years. The study also estimated random-parameter(mixed) ordered logit models to explore the heterogeneity in data. The most significant factor that was found to increase the severity of drivers' injuries in light-duty single-vehicle collisions is driving under the influence of alcohol or illicit drugs. Other significant factors, in decreasing order in terms of their significance, include driving on a highway curve, exceeding speed limit, lighting conditions, the age of the driver, and the age of the vehicle. In contrast, there were six factors that were found to be significant in only some years and not in all years. These six temporally unstable factors include the use of seatbelt, driver's gender, rural highways, undivided highways, the type of the light-duty vehicle, and weather and road surface conditions. These same factors were found by other previous research studies to be significant and stable predictors of drivers' injury severity in single-vehicle collisions.
