Friend or Foe… or Both?

Are autonomous and connected vehicles aggressors or allies, asks Yogesh Gautam

Automakers are making steady progress in bringing autonomous vehicles to market. Google and several OEMs – Ford, Nissan, GM, Tesla, and Volvo – have promised autonomous or semi-autonomous vehicles by 2020.  Autonomous Vehicles (AVs) are game changers – requiring no drivers, their benefits are unprecedented and can only be achieved when the vehicle drives by itself.

Connected Vehicles (CVs), on the other hand, can be manually or automatically driven.  They constantly broadcast signals and let other vehicles know where they are, at what speed and in which direction they are moving and thus avoid accidents.  If an accident is imminent the vehicle alerts the driver to take corrective action.  Let’s just remind ourselves of the benefits of both connected and autonomous vehicles.

Connected Vehicles

The two main advantages of CVs are communication with traffic signals (VxTS) and cooperatively interfacing with other vehicles. The main benefits of CVs at traffic signals include the redundancy in signal detection, and incremental gains in safety, and efficiency.  CV technology enables AVs to cooperate with other AVs in traffic maneuvers.

The CV program is a major USDOT initiative that began in 2003 and it is in the final phases of pilot deployments.  Based on the past pilots, the drivers find the technology useful and would be willing to pay for it.  The radio wavelength of 5.9 GHz, using dedicated sort range communication (DSRC), has worked well in the pilots.

The DSRC is well-suited for VxV and VxTS applications considering the short range (~300 m, 1,000 ft), low latency (time taken to rebroadcast the signal) and unit-to-unit direct broadcast. However, the in-vehicle connectivity for Internet, using cellular 3G/ 4G LTE, is a major initiative by OEMs which is making inroads, and as a result, autonomous vehicles are increasingly connected. The variant of Wi-Fi, cellular and other in-vehicle connectivity and in-cloud technology bring additional benefits and options that were not available in the past.

Autonomous Vehicles

Using advanced technology AVs are beneficial as well as sustainable. AVs employ an array of sensors – radar, Lidar, video, ultrasonic and laser – to map their surroundings in real time. An AV knows its precise location on a high definition digital map thus it can navigate the roadway network.  AV updates the base map as it encounters the objects of interest (traffic signals, signs and railroad crossings) in the field.

Although AVs’ performance can be enhanced by infrastructure support, their operation is satisfactory utilizing the existing infrastructure. Without having to rely on future infrastructure improvements, it is ready to drive from day one.


Vehicle x Traffic Signal (VxTS) Connectivity

At traffic signals, the signal timing information is suited for manually driven vehicles when directly provided to the driver.  For AVs with Traffic Signal Assist, the signal timing is an input to the vehicle and knowing the timings, the vehicle can safely adjust its speed to minimize delay and stops – FHWA’s GlidePath1 project is employing this methodology.  Also, in case of Electric Vehicles (EVs), the AVs can use automatic stop and start to achieve higher energy efficiency.  A DSRC-equipped vehicle can safely preempt the traffic signal to give signal priority to railroad, emergency vehicles, and transit. Currently, this is being implemented using proprietary hardware and software solution.

As AVs reach full automation, redundancy in the signal detection as enabled by DSRC becomes exceedingly important for system robustness. Presently AVs detect the signal indication color by video detection that is comparable to a driver seeing the signal color. Unlike video detection, DSRC is not affected by the occurrences of, for example, snow and ice obstructing the signal face, dark signal, knocked down signal head, light-flooded camera, dense fog, signal head oscillating or facing backwards.

The VxTS communication results in incremental but unique safety gains over AVs.  In mixed traffic AVs having 360 degree sensing up to 90m (300ft), can avoid most of the crashes that are attributable to driver error. However, some of the accidents that can only be mitigated by VxV communication include a driver rear-ending an AV, red-light running accidents and angled crashes due to limited sight distance, since the DSRC signal can be transmitted through solid objects.

An innovative application of vehicle-to-traffic signal application using existing standard technology such as the Internet and smartphones is the EnLighten app by Connected Signals ( The app tells the driver the time remaining before the green signal is illuminated.  BMW has partnered with Connected Signals and the app is available ina number of models.

However, the EnLighten app is for light duty consumer use only. The VxTS DSRC communication to be used in controlling the vehicles has more stringent requirements. As a result, knowing the critical signal timings with high accuracy in real time, the vehicle can achieve higher efficiency, and at the same time safely clear the intersection with high confidence.


VxV Connectivity

The main advantages of VxV connectivity are mitigation of accidents, cooperative lane changing, cooperative cruise control relay of traffic conditions – traffic incidents, work zones, congestion and hazards such as an icy bridge.  Given the 300m (1,000ft) range of DSRC signal, the relay of traffic conditions may require relay stations under light traffic conditions.

Cooperative lane changing, such as passing, merging, exiting and diverging results in safe and efficient operation, eg, the blind spot crashes are mitigated. Cooperative adaptive cruise control reduces the space between the two adjacent vehicles and thus increases the capacity. The vehicles operate as if in a platoon, increasing throughput at the traffic signals.

Irrespective of the automation level of other vehicles, AVs avoid the accidents entirely. On the other hand, the accident avoidance by CVs is limited since other vehicles need to have DSRC in increasing numbers.  Also, the DSRC signal needs to be an input to AV and bypass the driver who is responsible for most of the accidents. In fact, the manual alerts and AVs are incompatible – the DSRC mandate should give OEMs the flexibility in choosing between manual and automatic alerts.

Autonomous Vehicles and Connected Vehicles Status

At the present time, the AV space is the focus of wide interest and progress.  Here, the key is to realize the benefits of VxV connectivity in supporting AV without jeopardizing the progress being made in AV.  Many of the issues related to VxV communication, and especially because of the interaction with AV are as follows.

1     The vehicle automation is advancing at a fast pace. AV is a high priority with OEMs, and although many OEMs have promised full or semi AV by 2020, it remains to be seen what is meant by full or semi AV.
2     The in-vehicle Internet connectivity enabling smartphone-like features is quite important for OEMs.  And they want to bring in-vehicle connectivity sooner because the younger buyers’ purchase decisions are based on it.
3     National Highway Traffic Safety Administration (NHTSA) is expected to issue the final rule on DSRC in early 2016. Under the rule, the OEMs would be required to fit CV modules to all light vehicles made after 2019 – the estimates are based on a similar NHTSA case2.  Vehicle to Infrastructure Deployment Coalition, an advocacy group comprising the USDOT, AASHTO, State DOTs and the vendors, is determinedly pursuing deployment of VxTS connectivity.  This will demonstrate how vehicles equipped with CV modules will perform at connected traffic signals.


4     GM is testing connected vehicles in VxV dedicated spectrum and has promised to deploy DSRC VxV technology in its Cadillac CTS model from 2016.  OEMs participation in VxV and VxTS is expected to increase once NHTSA mandates DSRC.

There is synergy between AV and CV – CV brings additional and incremental benefits to AV.  CVs’ dependence on the driver diminishes its effectiveness in accident reduction.  Although AVs can operate with a high degree of confidence, AVs needs CVs’ attributes to achieve full automation.  Implementation of CV is a long-term, infrastructure-intensive undertaking.  AVs, on the other hand, without the added benefits of CVs, are ready for the drive from day one.   If the ultimate goal is a driverless vehicle, then the focus should be on the automated vehicle and how connected vehicle can support it.



2 NHTSA’s final rule on K.T. Safety Act, February 28, 1011 (Docket No. NHTSA-2010-0162)


Yogesh (Yogi) Gautam, PE, is a Traffic Systems Engineer with Illinois DOT.  The contents of this article reflect the views of the author and not the official views or policies of the Illinois Department of Transportation.