# Ride Comfort Prediction on Urban Road Using Discrete
## 1 Introduction  
Ride comfort is crucial to drivers and passengers as it is not only related to the ride quality but, more importantly, to driving safety and the health of drivers. On urban roads, short road segments and local irregularities further exacerbate ride discomfort. An effective and reliable prediction method of ride comfort will help drivers or autonomous vehicles improve riding experience and reduce the risk of accidents [1]. The prediction of ride comfort based on pavement roughness indices has been widely studied in recent decades because of their strong correlation [2; 3; 4]. Relative studies focused mainly on developing correlations between the ride comfort and the pavement roughness indices by means of simulations or field tests. In terms of ride comfort, the weighted root-mean-square acceleration (WRMSA) proposed in ISO 2631 [5] is the most commonly used index to characterize the effect of vibration on human comfort. WRMSA is capable of representing ride comfort over a relatively extended duration but struggles to characterize short-term ride comfort on brief road segments. In such instances, ISO 2631 also defines the maximum transient vibration value (MTVV) index for assessing transient vibration, which is better suited to evaluate ride discomfort resulting from road anomalies [6]. For pavement roughness, large amounts of indices have been proposed in past decades for the evaluation of roughness, taking into account vehicle-pavement interaction, the frequency contents of the road profile, and even road profile obstacles [7; 8; 9; 10]. Among them, the international roughness index (IRI) [11] is recognized and used worldwide as a standardindex for the evaluation of roughness. In addition, some other roughness indices or evaluation methods have also been made for specific scenarios, such as the bus ride index (BRI) for bus comfort evaluation [12], bicycle ride comfort evaluation [13], and the Being bump index (BBI) for airport pavement roughness evaluation [14]. [PERSON] et al. [15] provided a comprehensive summary of the prevalent indices utilized in pavement roughness evaluation, highlighting their respective properties. They underscored the significance of correlation adequacy with ride comfort, emphasizing its pivotal role in determining the applicability of a given roughness index. Drawing upon findings from simulations or field measurements, extensive research efforts have been dedicated to the investigation of correlations aimed at ride comfort prediction [16; 17; 18; 2]. [PERSON] [19] summarized the relevant studies in the correlations proposed in the last twenty years and revealed the following: (1) the IRI is the most commonly used index for ride comfort prediction because of its strong linear relationship with the WRMSA; (2) ride comfort prediction accuracy is sensitive to vehicle speed, and higher speeds result in higher WRMSA. Though IRI is reliable to use to predict ride comfort, due to the specific definition of IRI, it is difficult to characterize the roughness of shorter road sections. Therefore, existing research mainly focuses on longer road sections (such as highways or expressways) and with less consideration of short road sections and urban roads. For example, the road surface is more uneven at the intersections as a result of the deceleration and the brakes of vehicles, whereas the pavement condition is better on other sections. Thus, the existing correlations may be inappropriate to predict the ride comfort on urban roads. Some scholars [20] have proposed using probability distribution indicators to characterize the fluctuation of driving comfort on road sections, but still cannot accurately predict local discomfort. Additionally, current studies rarely take the combined effects of the left and right wheel paths into consideration. In the scenario of predicting ride comfort on urban short road sections, the main limitation of the IRI lies in its definition. The IRI is an average value that represents how significant the suspension response is at a particular distance.