Use of the emergency lane as third lane (Project T3) on Mestre Beltway

Luca Studer / 05 May 2017 14:02

ITS Domain(s):
Traffic management & control
Scale:
  • International
  • National
  • Regional
  • Urban

Description

Roads in the area of Mestre (Venice) represent the main bottleneck of the road network in the Italian north-eastern area.
The T3 project is based on the use of the emergency lane with bad traffic conditions. The aim is to improve, if necessary, the beltway capacity and it shall be achieved by:
o regulating the number of open lanes. The arrangement adopted shall be indicated by the variable message system;
o adjusting speed limits according to traffic conditions on the network.

Objectives of the project

On the one hand ITS projects aim at protecting human lives by reducing the number of accidents; on the other hand they aim at minimizing traffic jams by reducing traffic during certain time bands of the day.

The number of accidents (mainly small collisions) decreased thanks to the extension of safety distances as a consequence of traffic fluidification.

The T3 project aims at improving traffic conditions by making an optimal use of the available facilities resources. By increasing the road capacity, the project aims at making traffic conditions more homogeneous, i.e. at reducing the “stop and go”.

Systems and technologies applied

The T3 project consists in a dynamic use of the emergency lane on the beltway of Mestre, made possible through a series of interventions both on facilities and telematic.

Results/Lessons Learnt

Interventions on facilities can be divided into two types, i.e. interventions aimed at improving and extending the already existing systems and at carrying out new ones.

The former concentrate on improving the MARCO system by introducing new devices and functions, in particular:

  • improvement and extension of the existing video control subsystem;
  • extension of the optical fibre connection to cover the whole motorway network;
  • extension of the SOS system;
  • installation of variable message systems on the beltway to provide users with information on variable speed limits and on the use of lanes.

The T3 project includes interventions aimed at carrying out new facilities, which mainly are:

  • adapting the dimensions of carriageways: from the current two 3.75-m-lanes plus the 3.00m-emergency to three 3.25-m-lanes with adaptation of the related vertical and horizontal signs;
  • fixing of the pavement of the current emergency lane on the embankment sections;
  • carrying out of 22 lay-bys for emergency stops;
  • carrying out of emergency pathways for pedestrians linked through stairs on emergency lay-bys, useful for emergency operations and for leaving in case of emergency;
  • lengthening of acceleration and deceleration lanes to allow traffic flows to converge in safe conditions;
  • carrying out of passages in the traffic divider and conforming to norm of the central and side guardrail.
  • installation of about 1550 metres of new acoustic insulation barriers

Telematic interventions can be summed up as follows:

  • implementation of an AID system (Automatic Incident Detection) to detect accidents occurring along the whole beltway regardless of traffic and weather conditions, with delays of a few seconds;
  • implementation of a surveying system to detect the occupation of lay-bys consisting in dedicated telecameras and image analysis devices;
  • adjustment of the central software to manage speed control and lane use strategies when disturbing events occur (jams, works, accidents);
  • extension of the traffic surveying system thanks to 23 other sections;
  • extension of the user informing system thanks to new variable message systems, 3 telematic kiosks and a section of the website of the Autostrade di Venezia e Padova S.p.a. dedicated to real-time information;
  • extension of the video control system by introducing new telecameras, thus allowing to monitor the main critical points of both the motorway and the beltway.

Success story description

Safety

Potential and actual safety has increased on the infrastructure where the T3 system was implemented:

  • the number of accidents per direction has significantly decreased (- 57,7% eastbound, -49% westbound); even the number of collisions has decreased, both in absolute terms (-71% eastbound, -66,7% westbound) and as percentage on the number of accidents.

 

Number of accidents

Number of collisions

Percentage of collisions

 

eastbound

westbound

eastbound

westbound

eastbound

westbound

Pre implementation

78

49

69

33

69%

67%

Post implementation

33

25

20

11

20%

44%

Change

-57,70%

-49,00%

-71%

-66,70%

   

Accidents peaks have decreased at ramps and junctions, caused by “stop & go”, thanks to a better traffic flowing.

  • the standard deviation of hour speed has significantly decreased (-7,2% in winter and -43,7% in summer when the third lane was most frequently opened), thus indicating a higher evenness of traffic and a reduction of the potentially risky phenomenon of “stop & go”;

speed standard dev.

winter

summer

total

working days

non w. days

total

non w. days

working days

all day (average)

-4,5%

-3,8%

-1,0%

-38,8%

-34,3%

-43,1%

third lane opening time bands (average)

-7,2%

-4,7%

-2,9%

-43,7%

-34,5%

-44,1%

best performance per hour

-16%

-20%

-60%

-61%

-62%

-80%

  • vehicles linear density has significantly decreased (-31,0% in winter and -41,1% in summer) thus allowing an average increase in safety distances between vehicles.

linear density of vehicles

winter

summer

total

working days

non w. days

total

working days

non-w. days

all day (average)

-30,4%

-29,3%

-28,6%

-40,9%

-42,7%

-36,1%

third lane opening time bands (average)

-31,0%

-30,8%

-30,4%

-41,1%

-45,7%

-39,3%

best performance per hour

-36%

-35%

-38%

-49%

-50%

-48%

Effectiveness

The third lane was most frequently opened between 5-23 in winter and 5-21 in summer.

In the remaining time bands the third lane is less often opened with a frequency under 50%, with minimum frequency (lower than 10%) at night during winter.

Traffic flows have increased in the sections under control (+7,5% on average in time bands when the third lane was more frequently opened in winter, and +8,0 in summer).

The highest average increase was recorded in winter working days (+12,6%).

traffic flows

winter

summer

total

working days

non w. days

total

working days

non-w. days

all day (average)

6,6%

11,6%

-0,3%

6,1%

5,3%

11,6%

third lane opening time bands (average)

7,5%

12,6%

0,2%

8,0%

7,6%

12,8%

best performance per hour

16%

26%

6%

21%

18%

26%

The highest increase in traffic volumes was recorded on the sections under control with respect to the volumes registered at the Mestre barrier and on adjacent motorway networks. It confirms the further effect of the T3 with respect to traffic increase due to a general increase in the demand.

The different amount of traffic increases in winter on the several sections under examination indicates a substantial increase of short-distance flows which cover only part of the sections under examination. This result proves the improvement in the accessibility of the infrastructure on the part of local traffic using the beltway. Before the T3 implementation local traffic had to use other roads because of the high congestion on the beltway.

Flow speed has increased, especially in summer (+23,6%, corresponding to +15 km/h), and more clearly on working days. Journey time on the beltway has therefore decreased allowing users to save on journey time.

Speed limits imposed and indicated by VMS are generally observed, thus proving the effectiveness of their use in indicating speed limits.

flow speed

winter

summer

total

working days

non w. days

total

working days

non w. days

all day (average)

5,6%

4,8%

4,2%

17,5%

20,0%

13,9%

third lane opening time bands (average)

7,1%

6,3%

5,1%

23,6%

27,8%

17,3%

best performance per hour

16%

18%

9%

36%

44%

28%

Environment

The regularisation of flows and speed after the T3 implementation ensures an improved traffic flowing and the sharp decrease in traffic jams, which usually cause a particularly polluting way of driving.

The effect on the environment may therefore be considered positive, even if no quantity indicators for emissions and air quality were developed.

Partners
Start date
20-Mar-0000
End date
Status
Completed
Duration
3 months
Other links
Tags / keywords:
Safety Traffic data traffic management
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