83 Road crashes are serious concerns globally as they claim and cause more than 1.35 million fatalities and up to 50 million resulted injuries each year, respectively. Previous studies showed that the causes of road crashes are multifactorial, with human error contributed to approximately more than two-thirds of all road crashes, particularly in developing countries. One of the primary causes of vehicle crashes is failure to use turn signals by motorists. Although several studies have explored the use of turn signal among motorists in developed countries, limited studies have examined such risky behavior in developing countries, especially Malaysia. This paper aims to investigate the prevalence and characteristics of turn signal use among motorcyclists especially when changing lanes and turning at intersections, in Klang Valley, Malaysia. Video data of motorcycles in road trafc were recorded via instrumented research vehicle which made routine trips along selected driving routes in Klang Valley. The driving routes encompassed expressway, mixed with urban and interurban roads, as well as rural roads. The results reveal a signifcantly low overall percentage usage rate of turn signal among the observed motorcyclists at 41.1%. Furthermore, 60.9% of motorcyclists failed to signal when changing lanes, and 56.5% disregarded them while turning at intersections. The fndings provide vital information to the authority to develop proper policy and propose measures to increase compliance of turn signal use among motorcycle motorcyclists such as more targeted enforcement, widespread road safety campaigns and mandated utilization of technology-based solutions. Keywords: Motorcyclists; turn signal use; direction indicator; trafc safety; crash prevention; Malaysia Jurnal Kejuruteraan SI 3(1) 2020: 83-88 https://doi.org/10.17576/jkukm-2020-si3(1)-13 Turn Signal Use among Motorcyclists in Klang Valley, Malaysia: A Case Study Aqbal Hafeez Ariffin a *, Azhar Hamzah a , Mohd Syazwan Solah a , Noor Faradila Paiman a , Muhamad Syukri Abdul Khalid a , Noradrenalina Isah a , Khairil Anwar Abu Kassim a , Siti Zaharah Ishak a , Hisashi Imanaga b & Hajime Ishida c a Malaysian Institute of Road Safety Research (MIROS), 43000 Kajang, Selangor D.E., Malaysia b Japan Automobile Research Institute (JARI), Tsukuba, Ibaraki 305-0822, Japan c Japan Automobile Manufacturers Association, Inc. (JAMA), Minato-ku, Tokyo 105-0012, Japan *Corresponding author: aqbal@miros.gov.my Received 02 December 2019, Received in revised form 26 May 2020 Accepted 20 June 2020, Available online 30 September 2020 ABSTRACT INTRODUCTION ROAD CRASHES AND CAUSAL FACTORS According to the recent data released by the World Health Organization (WHO) in 2018, about 1.35 million people are killed and up to 50 million injured each year as a result of road crashes worldwide. From the fgure, more than 50% of road deaths are vulnerable road users, which include motorcyclists. The road safety situation in Southeast Asia (SEA) is also alarming, with the region recorded the second- highest rate of road death per 100,000 population (by WHO region defnition) after Africa (WHO 2018). With a high proportion of motorcycles on roads, more than 43% of road deaths in the SEA region were those of motorcycle users. In Malaysia, approximately more than 6,000 road deaths were registered yearly, with around 60% fatalities were of motorcyclists (Abdul Manan & Várhelyi 2012; RMP 2019). This situation is worrying as motorcycles accounted for nearly 45% (as in Jan-Feb 2019) of the total registered vehicles (RSD 2019). Among the main factors associated with motorcycle crashes are poor conspicuity and visibility due to their small size making them much harder to be detected by other road users (Radin Umar et al. 1995; Solah et al. 2013; Rahman et al. 2014; Micucci et al. 2019). Previous studies showed that road crashes are caused by multiple factors that involve human error with the interactions of vehicle and roadway factors (Robertson 1992; Shankar & Mannering 1996; Hendricks WHO 2006; Mohanty & Gupta 2015). In many road crashes, human- related errors and defciencies were the most frequently cited as the probable causal factors (Hurt et al. 1981; Petridou & Moustaki 2000; Green & Senders 2006; NHTSA 2008; Adanu & Jones 2017). Research also shown that majority of road crashes, especially in developing countries, were due to human error (TRL 1990; Gopalakrishnan 2012). Some examples of human errors and defciencies that led directly to road crashes include inattention/distraction, driver’s faults, and lack of skills. Ponziani (2012) in his study revealed neglecting the use of turn signals as one of the primary causes of vehicle crashes (estimated 2 million road deaths) and resulted in higher crash rates than distracted driving, for example, texting or using cell phones.