Computer system for calculating accurate estimations of traffic velocity in a road network such that the velocity data may be used by autonomous vehicles and/or by navigation systems of any vehicles to foresee road segments with low velocity and adapt a driving behavior accordingly, the road network comprising one or more road segments, the system comprising: a plurality of devices, each device operable to deliver speed measurement data corresponding to the speed of a traffic flow in the road network; and at least one computational unit, wherein each of the plurality of devices sends speed measurement data to the computational unit, characterized in that the computational unit is operable to calculate accurate estimations of traffic velocity in the road network by: - identifying, based on the speed measurement data, regions with varying sizes and moving boundaries under the condition that within each region of the regions a corresponding traffic phase p is constant, wherein each traffic phase is one of a free-flow phase, a synchronized phase or a wide moving jam phase, and wherein each region of the regions is defined as a part of a road segment of a length, wherein the identifying of the regions comprises: - calculating, from the speed measurement data, criteria probabilities P p i t x for each traffic phase p; - calculating, as the product of all criteria probabilities, the independent probability P p ′ t x for each traffic phase p; - estimating the uncertain probability P U ∈ [0,1], wherein P U describes a level of uncertainty in assigning (t, x) to any of the phases p; - taking into account the dominance of the wide moving jam phase; and - determining final phase probabilities P p; wherein P denotes probability; p denotes phase; x denotes a respective position along a respective road segment; and t denotes a point in time the vehicle was at the respective position along the respective road segment; and - calculating accurate estimations of traffic velocity (V E) in said regions based on the corresponding traffic phases. a plurality of devices, each device operable to deliver speed measurement data corresponding to the speed of a traffic flow in the road network; and at least one computational unit, wherein each of the plurality of devices sends speed measurement data to the computational unit, characterized in that the computational unit is operable to calculate accurate estimations of traffic velocity in the road network by: - identifying, based on the speed measurement data, regions with varying sizes and moving boundaries under the condition that within each region of the regions a corresponding traffic phase p is constant, wherein each traffic phase is one of a free-flow phase, a synchronized phase or a wide moving jam phase, and wherein each region of the regions is defined as a part of a road segment of a length, wherein the identifying of the regions comprises: - calculating, from the speed measurement data, criteria probabilities P p i t x for each traffic phase p; - calculating, as the product of all criteria probabilities, the independent probability P p ′ t x for each traffic phase p; - estimating the uncertain probability P U ∈ [0,1], wherein P U describes a level of uncertainty in assigning (t, x) to any of the phases p; - taking into account the dominance of the wide moving jam phase; and - determining final phase probabilities P p; wherein P denotes probability; p denotes phase; x denotes a respective position along a respective road segment; and t denotes a point in time the vehicle was at the respective position along the respective road segment; and - calculating accurate estimations of traffic velocity (V E) in said regions based on the corresponding traffic phases. - identifying, based on the speed measurement data, regions with varying sizes and moving boundaries under the condition that within each region of the regions a corresponding traffic phase p is constant, wherein each traffic phase is one of a free-flow phase, a synchronized phase or a wide moving jam phase, and wherein each region of the regions is defined as a part of a road segment of a length, wherein the identifying of the regions comprises: - calculating, from the speed measurement data, criteria probabilities P p i t x for each traffic phase p; - calculating, as the product of all criteria probabilities, the independent probability P p ′ t x for each traffic phase p; - estimating the uncertain probability P U ∈ [0,1], wherein P U describes a level of uncertainty in assigning (t, x) to any of the phases p; - taking into account the dominance of the wide moving jam phase; and - determining final phase probabilities P p; wherein P denotes probability; p denotes phase; x denotes a respective position along a respective road segment; and t denotes a point in time the vehicle was at the respective position along the respective road segment; and - calculating, from the speed measurement data, criteria probabilities P p i t x for each traffic phase p; - calculating, as the product of all criteria probabilities, the independent probability P p ′ t x for each traffic phase p; - estimating the uncertain probability P U ∈ [0,1], wherein P U describes a level of uncertainty in assigning (t, x) to any of the phases p; - taking into account the dominance of the wide moving jam phase; and - determining final phase probabilities P p; - calculating accurate estimations of traffic velocity (V E) in said regions based on the corresponding traffic phases.