Traffic information is very useful in planning and designing of road transport, ensuring efficient administration of road traffic, transportation agencies as well as for the convenience of road users. Traffic can be measured in terms of speed, density and flow. In this paper, we propose two different methods to measure traffic in terms of density and flow. The set up for the proposed traffic monitoring system includes a camera placed at a height from ground looking downward on the road, such that its field of view is perpendicular to the direction of motion of the traffic. The images of the road are continuously captured by the camera and processed to determine the traffic.The first method uses Gaussian Mixture Modeling (GMM) to detect vehicles. Density is calculated in terms of area occupied by the vehicles on the road. Another method of measuring the traffic flow is proposed that is based on calculation of edge points on a horizontal line drawn in the image. Both these methods determine the traffic flow in terms of number of vehicles per unit time. However, results show that the former works better for heterogeneous traffic, i.e. containing vehicles of different sizes. The third method to measure traffic is based on calculating its density in terms of area occupied by the vehicles on road. We have discussed the advantages and challenges of each method, and the results for different scenarios like city roads, highways etc have been presented.