# Study on Quantitative Expression of Cycling Workload
## 5 Discussion and Conclusions  
Cycling is an increasingly popular mode of transportation thanks to its healthy and environmentally friendly effects. However, a high cycling workload caused by an inappropriate design of the geometric elements and facilities of bikeways contributes to the rates and severities of bicycle accidents. Without a quantitative expression method and safe threshold values to determine cycling workload, it is hard to control the workload effectively; furthermore, it is difficult to reduce the concerning social and economic losses caused by bicycle accidents. In this paper, a cycling workload definition for dynamic cycling was proposed to reflect cyclists' feelings of safety and comfort while considering their formation mechanism. Based on the concept proposed here for cycling workload, a cycling experience interview survey, and interdisciplinary integration, a corresponding subjective scale was put forward; this scale categorized cycling workload into three levels--comfortable, a little stressful, and stressful. Furthermore, in accordance with the existing literature, the measurement techniques used for workload conditions causing physiological reactions were analyzed; HRV measurements and indicator LF/HF values were finalized to objectively quantify the cycling workload. In addition, a field cycling experiment was arranged to obtain a variety of cycling workload statuses by establishing various cycling widths, speeds, and bikeway edges to reflect typical bikeway characteristic scenarios. A quantification model was built to quantify cycling workload. Finally, the classification thresholds of three cycling workload levels were obtained using a CART algorithm, with the \(\Delta HRV\) threshold between \"a little stressful\" and \"comfortable\" being 19 and that between \"a little stressful\" and \"stressful\" being 79. Our research results, which provide support for the method of measuring cycling workload, comprised a physiological metric of \(\Delta HRV\) combined with a subjective scale. This method of quantitatively expressing cycling workload can be used for measurement and evaluation of the effects of bikeway characteristics such as lane width and separation facilities. This can contribute to the design of safe and comfortable bikeways and their operational management to reduce the risk of bicycle accidents and provide theoretical and practical support for determining the reasonable technical parameters for bikeway characteristics. Additionally, it can be conducive to the formulation of policies that aim for carbon neutrality; such policies will promote the use of healthy and sustainable bicycle transportation, particularly in areas where bicycle transportation is in great demand for commuting purposes. Moreover, if cycling workload is kept within a comfortable range, \begin{table}
\begin{tabular}{c c} \hline \hline
**Cycling Workload Classification** & **Threshold** \\ \hline Normal workload (safe, comfort) & \(\Delta HRV\leq 19\) \\ Higher workload (safe, a little stressful) & \(19\less\Delta HRV\leq 79\) \\ Higher workload (stressful) & \(\Delta HRV>79\) \\ \hline \hline \end{tabular}
\end{table} 
Table 6: CART classification thresholds. Figure 8: CART algorithm classification diagram. then accident risk will be more easily controlled, since high cycling workload--i.e., with \(\Delta HRV\) values over 79--can result in a higher risk of bicycle accidents, which cause severe life, social, and economic losses. By utilizing the quantitation method and classification levels for assessing cycling workload that were obtained in this research, the indicator threshold limit values of bikeway characteristics--which ensure cyclists' safety and comfort (meaning the conditions ensure that cyclists' \(\Delta HRV\) values are within a level of safety and comfort)--can be inferred to guide future safety design standards for bikeways. For already-built bikeways, these limit values can be used to assess the safety operation conditions for further improvement.