Traffic calming devices should be installed only in conformance to the established design criteria, in effect at the time of their installation, and if all of the justification criteria are met. Study by Rahman et al. [11] reveals that most cities in North American are having a warrant based system to check the suitability of traffic calming device. It was found that the budget constraint is the most important reason to prioritize traffic calming projects while political intervention is the main drawback of the process. If it meets all of the justification criteria, then it will be rated and prioritized according to other criteria, such as traffic volume, speed, accidents, and petitions [9] . As with any traffic calming device, additions, alterations, or removal of any or all traffic calming devices may occur at any time if conditions warrant. In fact, the application of traffic calming could be vary among places. A technical resource developed by James et al. [15] is an example of guidance for the development of traffic calming programs, which compiled the do’s and don’ts of traffic calming. Kojima et al. [16] found the effective speed hump installment by considering vehicle speed, noise, and vibration as well as roadside installment.

As an example, in the United States, although the Federal Highway Administration specifies standards and guidelines through the MUTCD, individual state and local agencies can provide variations or additions to these standards [17] . Another example comes from Asia. Indonesia has speed hump standard as well, while in fact, this standard was not fully implemented by community. This standard was developed by Departemen Pemukiman dan Prasarana Wilayah [18] , where it was adopted from UK Department of Transport.

Based on these facts, it was difficult to formulate definitive conclusion about the effectiveness of traffic calming devices [19] . In practice, there had been few problems which originated from traffic calming devices [20] , like emergency response concerns, violate civil rights such as segregate communities along racial and socio-economic lines, violation to clean air act as a result of fact that the project of humps increased emissions, complaints from the disabled community, and possibility of conflict among communities.

At present, the capital city Dhaka is the most claimed traffic congestion city in Bangladesh, since in general; Bangladesh doesn’t meet the required transportation facility as well as transportation safety for the citizens [21] . Traffic calming in Bangladesh illustrates a range of practices, such as speed hump, speed table, choker, chicane, pavement marking, or textured and colored pavement. Even though, traffic calming warrants must be met before implementation of traffic calming devices but no set guidelines and criteria was found in Bangladesh at present.

Over the last few years, increasing number of motorized vehicles, vast population, and insufficient budget for the improvement of transportation facility and neighborhood safety have approached the country with issues of speeding and cut-through traffic. Historically, these situations could only be addressed by the use of police enforcement or speed humps. An expanded menu of options was required to address these issues. Requests for utilizations of traffic calming measures have been proved to be effective enough to manage the intolerable congestion of Dhaka city as well as the whole Bangladesh to meet the present traffic issues.

Presently in Bangladesh, few agencies are working on road safety, though there is very little practice observed in case of Traffic Calming. Traffic calming regulations are required to provide local highway authorities with the necessary powers to construct speed reduction and other measures for traffic calming that are not otherwise clearly authorized. Provision may need to be left for detailed specifications via ministerial regulations.

National Road Safety Strategic Action Plan 2011-2013 is the 6^th plan in Bangladesh [1] , where the first road safety action plan for Bangladesh (1997-1999) was approved on 1st February, 1997. There are nine individual sectors identified for road safety activities: National road safety council, Accident data system, Road engineering, Traffic legislation, Traffic enforcement, Driver training and testing, Vehicle safety, Education and publicity, and Medical services. Planning, management, and coordination of road safety is planned to be done by a specified framework as appears in Table 1. Road Safety Division of RHD (Roads and Highway Department) is responsible for permission of installation of a new Traffic Calming Device, while NRSC (National Road Safety Council) involved with decision making process of Traffic Calming Device. BRTC works to research on safety considerations for bringing harmony in the operation of

bus and truck services. Inclusion of road safety component in all important road projects of RHD and LGED (Local Government Engineering Department) is a part of strategic development plan. ARI (Accident Research Institute), BUET (Bangladesh University of Engineering & Technology) works on Development of a multimodal safe transport system in Bangladesh through Education, Research, Training Investigation, and Consultation. Research and investigation to identify the accident contributory factors and their remedial measures among which Traffic Calming Device are some of the major components. MOC (Ministry of Communications) is fully responsible for supervision of all the activities of these agencies.

In Bangladesh, the concept of traffic calming devices is not very widely used. It is not very much practiced in the neighborhood in Dhaka city and other part of the country. Thus, it has very low impact in Bangladesh. Speed hump or speed bump are the most common devises used in places in Dhaka city, besides the application of rumble strip used in highways. At present, in Bangladesh still there is not available national policies and design guidelines of traffic calming devices yet. It is argued that many other types of traffic calming measures could be tried to be implemented to increase the traffic safety in the neighborhood. It is also believed that now is the time to formulate a plan and set a national policy to make the neighborhood safer and reduce the risk of accident among the city roads and streets.

Lack of standard or guideline about traffic calming results in several problems. It is argued that the main concept of placing Rumble Strip was to attract attention of the driver so that the vibrating due to rumble strip reminds the driver that she/he needs to drive carefully. It is necessary in some places of the highway where pedestrian crossing rate is high due to the presence of school, college, or markets. But, many people requested to remove the rumble strips and replace it by other means like foot over bridge. It happened as there is no set guideline or criteria nationwide.

Three types of road in Dhaka city are considered, where the locations are Mirpur-1, Kazipara, Mirpur-7, Mirpur-11.5, Mirpur-12, Mirpur-14, Manik Mia Avenue, or New Airport Road. These sites are selected based on population density, number of vehicle movement, or pedestrian generation. Results of survey are presented in Table 3, while Figure 1 shows variation of speed hump in the field.

There is no distinct Government policy and also no set guide lines with the

concern authority to implement traffic calming devices, as well as to evaluate the sensitivity of the standard, justification, and appropriateness of the devices. It was found that due to lack of knowledge regarding the strengths and shortcomings of traffic calming devices, neighbor is less sensitive to the standard, justification and appropriateness of the Traffic Calming Devices. The situation is explained by the variety of dimensions of the devices as appears in Figure 2, Figure 3, and

Figure 4. As Dhaka City is running out of its capability in case of infrastructure to support its population, the in situ need to meet the local necessity overrules the evaluation of the justification and appropriateness of the devices. The result of interview survey with different government organization tells that there is no set procedure to guide the implementation of traffic calming device in Bangladesh. The current practice was guided only by the concerned of road construction authority.

From questionnaire survey, it was found that there are a vast variations in the response from the point of view of respondent. Variation is also detected for different types of road. The comparison results are provided in Table 4. For the question which deals with the suitability of the placement of the traffic calming device at distribution road, 56% of respondents state their agreement. High proportion (86%) of the respondents state that the devices are suitable in arterial road, while on the contrary, 89% of respondents state their disagreement of the placement in local road.

From Table 4, it can be shown that users who used arterial road seem to be more familiar with the dimension of the measures. On the contrary, users in

distributor or local seem as not familiar with the dimension. Users express that noise and vibration are the most problematic matters with the implementation of traffic calming. This exists in all road classification. It is interesting to know that users in all road classification state that the measures produce congestion as mild. Respondents seem to be in agreement that the implementation of traffic calming did not consume higher fuel.

Binary logistic regression was employed to reveal the residents compliance about traffic calming device and the reasons behind. The dependent variable of the model is the resident’s opinion about the suitability of placement of traffic calming device, where the value of one represents agreement for suitability and zero vice versa. Parameter estimates are described in Table 5.

The chi squared of the model has very small p-value, i.e. much lower than 0.05, which means the independent variables play a significant role in the decision of the suitable placement of the traffic calming device. The significance (p-value) of Hosmer Lemeshow test is much bigger than 0.05, which means the

failure to reject the null hypothesis that there is no difference between observed and model predicted values. This statistics imply that the model’s estimates fit the data at an acceptable level. The percentage has a value of 74.7%, which implies a good fitting model. Thus, it can be inferred that the model is well fitting.

The model found several significant variables, namely the dimension of traffic calming devices, comfort in using devices and smoothness in riding. It can be inferred that respondents have a focus on the comfort when passing devices. Respondents are not in favor with issues of environmental or safety yet at present. It reveals a challenge for the government to provide devices that is suitable with the expectation of the users, while at the same time providing devices that people can learn and experience ideal devices.

Based on the findings from the field survey and responses from the users, some recommendation can be provided as a way to improve the implementation.

A discussion with the road agency revealed that there is no standard of application process to implement traffic calming. In order to develop a standard, efficient, and effective implementation, thus a standard process is needed. Hence, the first recommendation is the establishment of a standard request or application process. A small cell can be formed in the City Corporation to inform if someone in the residential area feels that there should be a traffic calming device for safety purpose. A national chain of organization seems as not suitable in developing cities at present, so a cell can serve the purpose to some extent in more efficient way.

Related with the first recommendation, the second recommendation is to develop a standard evaluation, installation, and removal process. If a request is received, then concerned engineer from the City Corporation can pay a visit to the area and evaluate the request of the traffic calming device. Regarding the installation process, a standard and feasible timeline needs to be set and regular repair and maintenance should be done like the road maintenance schedule. Moreover, for removal procedure, some parameters might be needed to be set prior the removal of traffic calming device as a response to the received complaints received from different users.

Furthermore, for future development, it is recommended to employ field data collection to judge the user responses about the existing devices and also to formulate a future guideline for installation. This is the third recommendation. Data obtained both from field survey and questionnaire survey can help to compare the salient aspects of presently constructed traffic calming device with the standard speed hump. The result can be used in future to modify the present dimension and improve the user satisfaction in using the traffic calming device by placing them in the correct location.

In term of institutional matter, the fourth recommendation can also be provided. Steps can be taken so that the problems of traffic calming can be solved by integrating the agency already existing in the country. The agency should be integrated are BRTA (Bangladesh Road Transport Authority), DTCB (Dhaka Transport Coordination Board), MOC (Ministry of Communications), ARI (Accident Research Institute), RHD (Roads and Highway Department); BRRL (Bangladesh Road Research Laboratory), LGED (Local Government Engineering Department).

The fifth recommendation is public education about the measure. Survey shows that most users did not familiar with the dimension of traffic calming (Table 4). Less familiarity exists in local areas. Thus logically, it can be inferred that majority of citizen in Dhaka city are not aware of the pros and cons in using traffic calming. It is also understandable that the city corporation there is a lack of knowledge about the importance of traffic calming device. Thus, as a way to improve the understanding and change the behavior of users, the responsible agency can take steps to educate the community about various aspects of traffic calming devices. From this education it can be expected positive responses from the community, which in the end will improve the effectiveness of the device.

Furthermore, from the engineering point of view, some suggestions can also be provided as presented in Table 6. In most of the cases, the height of speed

hump of Dhaka city needs to be reduced, the width needs to be increased, and the slope needs to be milder. On the other side, traffic sign and markings are needed to be installed in all the locations, while regular supervision and a periodical maintenance should be done. It is also important to state that necessary actions should be taken to educate the neighborhood respondents and pedestrians about the significance of speed hump as a means of traffic calming device.

Several lessons can be drawn from the experience in implementing traffic calming in developing city like Dhaka city as follows:

a) Before the implementation of traffic calming, it is needed to have socialization to the community regarding the characteristics, benefits, and impacts. Successful socialization will increase public awareness regarding the measures. This awareness is fundamental for the sustainability of the traffic management scenarios, as it can be expected as a first step to implement another measure.

b) As there is a capacity and capability limitation in developing cities to manage comprehensive and well-designed traffic management measures, thus a local specific measures is needed. Traffic calming devices that is designed and adjusted to be suitable with local characteristics is more preferable, rather than just copied and imported from developed cities. It is understandable to learn from developed cities who have well managed and researched, but adjustment is a must.

c) Setting up a unit to specifically responsible for the development of traffic management measures will be beneficial. This unit will responsible in researching and developing the measures and find a suitable measures with the local context. This unit will maintain the sustainability of the development, rather than hand it to transportation department which is responsible for a very broad matter.