By Topic

Intelligent Transport Systems, IET

Issue 4 • Date December 2009

Filter Results

Displaying Results 1 - 7 of 7
  • Simultaneous interaction with in-vehicle systems while turning left: comparison among three groups of drivers

    Page(s): 369 - 378
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (394 KB)  

    The growing introduction of new technologies inside vehicles represents a set of extra information sources. Its use can interfere with the driving activity and induce performance decrements. An on-road experiment was conducted to investigate how drivers reacted to the simultaneous interaction with in-vehicle systems. Forty-eight subjects (elderly, reference and novice) participated in the tests. They were asked to interact with one (road guidance system) or two (road guidance system and mobile phone) on-board devices. Their performance was evaluated for the turn left manoeuvres and main effects of system conditions were revealed. The simultaneous interaction with both in-vehicle systems induced participants to some performance decrements on the driving task: higher number of late activations of the turning indicator; lower mean speeds before the intersection; lower values of instant speed at the beginning of the turn manoeuvre; higher steering wheel variability; activations of the braking pedal with less pressure, later, and performing a higher number of strokes; and also less glances towards important areas of the environment. No significant difference was observed for the guidance task. The comparison between driver groups' performance did not reveal enough significant differences in order to draw a general conclusion. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Analysis of drivers' preparatory behaviour before turning at intersections

    Page(s): 379 - 389
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (579 KB)  

    This study analyses naturalistic driving behaviour before making turns at intersections. Instrumented vehicles recorded drivers' preparatory behaviour, including moving the right foot to cover the brake pedal and activating the turn-signal, while approaching the turning point on public roads. Data were analysed for relations between driver preparations, different traffic conditions (with or without forward and/or following vehicles) and the intersection type and turning direction. The results suggest that braking began closer to the target intersection when driving with a vehicle in front, independent of the number of traffic lanes or the turning direction. In contrast, the onset of braking occurred further before the intersection when drivers had a forward vehicle while approaching intersections after curves, where drivers cannot readily determine the distance between their vehicle and the turning point until just before the intersection. The presentation timing of vehicle navigation systems for each traffic condition is discussed based on the road structures of turning points. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Driver behaviour when using an integrated advisory warning display for advanced driver assistance systems

    Page(s): 390 - 399
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (362 KB)  

    With the increasing amount of safety features that are being introduced in our vehicles, research on warning design has suggested that advisory warning information may benefit driving performance. This simulator driving study compared driver's performance using an integrated advisory advanced driver assistance system (ADAS) display based on ecological interface design (EID) combined with critical warnings to three ADAS with warnings of a critical character only. Results show that drivers drove with safer distances to vehicles in front when they received combined advisory'critical warnings compared to critical warnings only. Further, participants maintained better lane positioning during both the critical and combined ADAS conditions compared to baseline driving. In addition, participants found the combined warnings made them more aware of the traffic situation than when driving with critical warnings only and that the display helped them notice potential dangers in the traffic environment. These results suggest that providing drivers with advisory ADAS information can be a good complement to the critical warnings found in vehicles today and that a combination of these warnings, if correctly designed, may benefit both driver performance and driver acceptance. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Probability-based bus headway regularity measure

    Page(s): 400 - 408
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (429 KB)  

    In frequently serviced bus routes passengers are more concerned about bus headway regularity than actual punctuality of bus arrival to the schedule. Buses arriving within very small (bus bunching) or very large headways are of particular concern and much less desirable. In this study, a time-point (stop) level probability-based headway regularity metric to measure bus service reliability is first formulated as a function of bus dwell time, number of stops into the trip, passenger activities (i.e. arrival, boarding and alighting) and expectation (or tolerance) of bus headways. The proposed metric is then applied to evaluate a Chicago Transit Authority bus route by using automatic vehicle location (AVL) data. It is found that headway regularity during a bus trip is closely impacted by dispatching headway. Furthermore, the time-point level service reliability declines as passenger activity levels increase or as the maximum passenger anticipated headway decreases (i.e. passengers become more demanding of frequent bus services). The case study demonstrates that the proposed probability-based headway regularity measure provides an operationable metric to transit agencies in terms of improving the transit service to meet passengers' expectation and thus increase ridership. Lastly, this study demonstrates another important application of the AVL/APC data. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Joint channel tracking and intercarrier-interference equalisation for vertical Bell Labs layered space time-orthogonal frequency division multiplexing in vehicle ad hoc network

    Page(s): 409 - 418
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (951 KB)  

    Vertical Bell Labs layered space time-orthogonal frequency division multiplexing (VBLAST-OFDM) systems can achieve high spectral efficiency in quasi-stationary links and with channel state information (CSI) matrix knowledge. Owing to the high speeds of nodes in vehicle ad hoc network (VANET), the channel is fast fading thus raising the need for channel tracking. Furthermore, inter-carrier interference (ICI) causes an error floor at high signal-to-noise ratio (SNR) even with perfect CSI knowledge. In this paper we investigate channel tracking and ICI mitigation for VBLAST-OFDM. The analysis of ICI shows that it increases with speed, number of subcarriers and/or number of transmit antennas. The authors then introduce a simple channel tracking algorithm for VBLAST-OFDM. Simulation results show that our algorithm reduces the bit error rate (BER) of a 2 times 4 VBLAST system by 10-2 at 40 dB SNR and 100 km/h speed compared to obtaining a channel estimate from a training sequence only. The change in the channel response is estimated using the channel tracking algorithm and then passed to an ICI equaliser to enhance performance and reduce the error floor caused by ICI at high SNR. Equalising five pairs of subcarriers gives 4 dB improvement for 2times4 VBLAST at 180 km/h relative speed. The performance is enhanced as more subcarriers are included in the ICI equaliser at the expense of increased receiver complexity. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Review of urban traffic management and the impacts of new vehicle technologies

    Page(s): 419 - 428
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (303 KB)  

    Traffic congestion is a growing problem in most urban areas across the world. In recent years, the problem has often been tackled by management of existing capacity rather than the traditional concept of more road building. This requires efficient traffic management tools and has led to widespread implementation of advanced traffic control systems integrated within a wider urban traffic management (UTM) environment. UTM systems collect data from various sources, process and manage the data and use this information to implement various measures to manage traffic. While infrastructure-based UTM systems continue to develop, there is now also a rapid market-driven development of vehicle technologies and in-vehicle driver support systems. Driver information and satellite navigation (sat-nav) systems are two examples already in widespread use, whereas other applications under research and development include intelligent speed adaptation (ISA), adaptive cruise control (ACC) and various other safety-related applications. This study will firstly present state-of-the-art reviews of UTM and in-vehicle systems. It will then discuss the potential impacts of new in-vehicle systems on UTM and opportunities for beneficial cooperation between the two. The research described in the study has been undertaken within a collaborative project FUTURES, funded by the Engineering and Physical Sciences Research Council (EPSRC). View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Simulation-based performance analysis and improvement of orthogonal frequency division multiplexing - 802.11p system for vehicular communications

    Page(s): 429 - 436
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (446 KB)  

    In this study, the physical layer (PHY) of the upcoming vehicular communication standard IEEE 802.11p has been simulated in vehicle-to-vehicle situation through two different scenarios. IEEE 802.11p wireless access in vehicular environment defines modifications to IEEE 802.11 to support intelligent transportation systems applications. The standard is being considered as a promising wireless technology for enhancing transportation safety and provides safety-related services like collision avoidance and emergency breaking. At first, this includes data exchange between high-speed vehicles and between the vehicles and the roadside infrastructure in the licensed ITS band of 5.9 GHz. Performance analysis of PHY model has been evaluated into different propagation conditions (AWGN, Ricean and Rayleigh fading). In particular, bit error rate (BER) and signal to noise ratio for all the data rates have been estimated. Simulation results reveal that our system can efficiently mitigate inter-symbol interference and inter-carrier interference introduced by multi-path delay spread in our high mobility environment but against frequency-selective fading BER values are on to increase. To overcome this problem, the authors propose to use a different value of guard interval (3.2 s). Our initial results indicate that the performance with the larger cyclic prefix outperforms the performance of the initial value in our mobile channel profiles. Moreover, the authors investigated in which way the Doppler spread affects the performance with regard to the transmission distance. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.

Aims & Scope

IET Intelligent Transport Systems is an interdisciplinary journal devoted to research into the practical applications of intelligent transport systems and infrastructures.

Full Aims & Scope

Meet Our Editors

Publisher
IET Research Journals
iet_its@theiet.org